Who’s There?

Ping.
Ping Who?
Ping I just knocked a hole in your piston….

Engine Knock, Fuel Octane and other myths

Thing One: Never use higher Octane fuel than the engine needs to prevent knock.

I’m going to try to greatly simplify a very complex topic here. They write encyclopedias about this stuff. I’m going to try to keep it to a few pages.

What is Knock/Ping?

When the engine is running normally, the spark plug fires and the flame spreads evenly thru the cylinder. The mix burns evenly until consumed. When the engine Knocks or Pings it means the fuel was set off at the wrong time and/or the fuel was set off from multiple sources. Both conditions are bad for the motor and rob you of performance and fuel economy.

What causes it?

There are many things that can cause it. Most of them you can and should fix.
Here’s a list of common items. (In no particular order.)

• Over advanced ignition timing. (Very easy to do with mechanical distributors but still possible with electronic ignition.)
• Vacuum leaks or EGR problems. (These are way more common than people think.)
• Exhaust leaks. (Even small upstream leaks can screw up O2 sensor accuracy.)
• Wrong spark plugs or other bad ignition parts.
• Carbon buildup in cylinders. This alters engine compression and can create hot spots.
• Engine sensors dirty/bad or damaged sensor wiring. If a sensor is lying to the ECM the car will never run properly.
• Compression increased as a result of engine or head rebuild. (This can be intentional or a side effect.)

What is Fuel Octane Rating?

That number you see on the pump comes from a bunch of tests that determine how much the fuel helps resist engine knock. The higher the number the more it resists knock and it usually means the fuel is also less volatile. This last bit is the big rub… Less volatile fuel will often perform worse, not better as many people think. How much you may notice this depends on the specific engine in question. In any case, using more Octane than needed will not increase engine performance. Higher-octane fuel sells for more than regular fuel. Compared to most 87 Octane fuels, you pay 10-20 cents more per gallon for a product that costs them almost nothing more to make. That extra dollar or two per tank can add up really fast. Why spend it if you don’t have to… The carmakers all list the minimum Octane rating for fuels in the owner’s manuals. For most Fiero I’m pretty sure it’s 87 Octane. (I know the 87 owners manual lists 87 for both the 4 and 6 cylinder.) Oh, and the factory 2.8 has lower compression than the 4 cyl, so don’t go thinking bigger engine means more Octane. (2.8 is 8. something:1 while L4 is 9:1) Even motors with 100,000 miles or more can run the specified Octane if they are in good shape. Mine has over 150,000 miles and is running wonderfully on 87 Octane fuel. (Even WaWa fuel that is usually one of the lowest priced fuels around the region.) Note: Someone in the forums pointed out the European Octane ratings are higher than the U.S. numbers. Keep in mind other regions of the world use different methods and rules for grading fuel. While the European Octane number might be higher, that doesn’t mean they are automatically better than U.S. fuel at preventing knock.

Bending the rule, additives in Pump Fuel

All U.S. fuel is required by the EPA to have cleaning additives in it. Fuel meeting the minimum requirements is perfectly fine for most cars. Some fuel vendors promote their fuel based on the additive package. These additives won’t add power so much as restore or maintain it by removing carbon and dirt. These additives have contributed to confusion over octane ratings. These cleaning additives, which are unrelated to Octane rating, may help performance in some vehicles. This can be a function of brand, grade, or both. Some brands use the same additive package in all grades of fuel, while others put the “good stuff” only in higher grades. As an example, Texaco puts “Cleansystem3®” in all their fuel. Other brands may put their best additive package only in premium grades. What results you’ll get from any additive packages will depend greatly on the condition of your engine. None of them are likely to clean up a really dirty motor but they may help an engine expel minor carbon buildup and other dirt. Some no doubt do this better than others. Other than cost, it won’t hurt anything to shop fuels based on their additive package. If one product works better for you than something else that’s great. Otherwise don’t buy more than you need. To use Texaco again… Since they put Cleansystem3® in all grades, you’d still run the lowest Octane fuel the engine will take. If Texaco 87 Octane fuel works, their 89 and higher isn’t going to do anything but cost more. (Texaco is just a handy national brand for an example… I use a regional brand most of the time.)

The car knocks/pings…

We’re talking generally stock engines here. Even a regular rebuild should run on the OE octane or maybe one step higher. Obviously if you’ve done a big build up or super/turbo setup, you could need more octane. If a car that was built to run 87 Octane only runs on 90+, the engine may just be dirty or you could have mechanical problems. If the car knocks even on the highest Octane pump fuel you almost certainly have engine problems that need repair. These are some things I look for when an engine knocks. Triple check for vacuum leaks. Even a tiny leak can lean out a cylinder enough to cause knocking without tripping ECM errors. (You’d be surprised how easy it is to have a vacuum leak that only messes with one cylinder.) Check the cooling system very carefully. Knock/Ping can also be an early sign of overheating. Don’t assume the temperature gauge is correct. (Even if it is correct, don’t assume there are no cooling problems. A common problem here is a head gasket installed wrong. This can make some cylinders hot even if coolant temp reads ok on the gauge.) Check timing on distributor motors very carefully. The difference between knocking and not can be just a couple degrees of advance. (Defective or improperly configured Mechanical Distributors are great for this.) Use OE EGR valves (GM, AC Delco, Motorcraft, etc.) whenever possible. If you must use a “universal” style valve, make sure it’s a good brand. A crappy EGR valve can really screw up an engine. (I have seen aftermarket valves die in as little as a year.) Is the engine suffering carbon buildup? You might want to try one of the carbon removal processes. Carbon buildup can be the result of past fuel system problems and other things. It usually won’t go away without help. Is the engine sucking oil? This can both alter the octane of the mix inside the engine and cause carbon buildup. It’s probably time to rebuild some or all this engine or find another. Higher Octane fuel or carbon removal is at best a temporary fix. 87-88 Fiero L4 motors with DIS may need a different PROM in the ECM. GM had an update to tweak ignition timing a bit. (The new PROM numbers are in DIS notes. This kind of stuff is common with ECM/PCM controlled motors.) This should be considered ONLY AFTER all other mechanical items are checked out.

An example

Awhile back, my car started knocking under certain load conditions. (87SC L4 w/ DIS) I’d also lost some fuel economy. This went on for weeks and since the problem wasn’t consistent, it was really a pain to find. It did it even on 90+ Octane fuel. (Since it hadn’t done this previously, I didn’t think the PROM update would help.) In searching for a vacuum leak, I took off the EGR to see if maybe the middle of the gasket had partly blown out. (A common problem with this type of EGR setup.) The EGR wasn’t that old, and like many aftermarket units not easy to test. Since it wasn’t very old I didn’t really expect it to be bad but just out of habit I checked to see if the pintle was moving ok while it was off. It wasn’t moving at all… It turned out that the 2-year-old aftermarket EGR valve had failed totally. It had jammed in such a way as to not open and still leak slightly. (It never set any kind of code in the ECM during all this.) The spring in the top had actually broken and you could hear it rattling around when shaken. Replacing the EGR with a good used GM valve solved both the knock problem and cranked fuel economy back up to 26 mpg even in really crappy traffic. (The EGR gasket cost about a dollar.) The lesson, yet again, is never to assume recently installed parts are good.

Fuel additives

Octane Boosters and Cleaners

Octane boosting additives don’t help much except maybe for when you have a modified/race engine and can’t find suitable fuel at the pump. A stock vehicle that won’t run on pump gas has something wrong. Octane booster products, like higher Octane fuels, usually will not increase performance. How much, if anything, a cleaning product does will depend greatly on how messed up the engine is. Don’t expect any miracles from most of them. Even professional cleaning products may not remove heavy buildup. Some add in Octane boosters and cleaning products may actually damage the older styles of port fuel injectors used by GM and some others. In the older injectors, used thru the late 90’s, the solenoid coil is exposed to the fuel. (This helps cool the coil.) Most products are probably ok but make sure they are used as directed on the container. Mix them stronger than directed and they might eat your injectors. (The newer GM injectors are redesigned and do not expose the coil to the fuel just because of this problem.)

I’ve heard fuel changes by season….

Yes fuel does change by season and it also changes by city and region. This double whammy can make buying fuel quite confusing. If you suddenly drop or gain 2-4 MPG, you might be a victim of Reformulated or Oxygenated fuel. In some vehicles these fuels may also induce knock/ping that forces you to a higher, more expensive, grade of fuel. What many people call Winter Gas is defined as Oxygenated or Reformulated Gas (RFG) depending on where you live. They are supposed to reduce air pollution. These fuels contain MTBE and other chemicals to increase the oxygen content of the fuel. They cost more, often cause odd problems, bite performance, and you get less MPG. There is little you can do about the problems caused by RFG and Oxygenated fuels. On HEI engines, try retarding the timing very slightly if you have ping/knock.

Acceptable Alcohol Fuel Content

Methyl Tertiary-Butyl Ether
Fuel containing Methyl Tertiary-Butyl Ether (MTBE) may be used, providing there is no more than 15% alcohol by volume. MTBE is under investigation in many places. Some states are likely to ban it in future. MTBE is intended to reduce air pollution but has been shown to be a serious problem when it gets in the water. Small amounts of MTBE can pollute large amounts of water and the stuff is hard to filter from drinking water.

Ethanol
Fuel containing ethanol (ethyl) or grain alcohol may be used, providing there is no more than 10% ethanol alcohol by volume. Ethanol plays a roll in Octane rating and pollution control. Its presence in motor fuels is likely to increase greatly as MTBE (Methyl Tertiary Butyl Ether) is phased out in many regions. Higher concentrations of Ethanol will alter the fuel beyond what the ECM/PCM can deal with, and may be too strong for some fuel system parts to handle. Pre-computer engines may need considerable carburetor and distributor adjustments to run right.

Methanol
GM recommends against any methanol use. It can damage the fuel system parts. (Nearly all carmakers say stay away from methanol even now.) “Dry” gas typically contains Methanol but not enough to hurt anything. Fuel containing methanol (methyl) or wood alcohol may be used, providing there is no more than 5% methanol by volume. Use of fuel (gasohol) that contains more than 5% methanol can corrode metal fuel system components and damage plastic and rubber parts.

Here are some interesting incites into the Iron Duke’s performance potential.

by: Gary Ohst

>> I was hoping anyone could tell me what the difference is between the SD valve cover and the stock 2.5. Specifically is the bolt pattern the same and is there room for needle bearing rockers?<<

The bolt pattern is the same for all years. There is plenty of room for valve train mods. That cover is too tall to fit under the stock air cleaner intake housing. There are no provisions for a PVC valve port. It would require some mods to fit on a production motor with all emission control hooked up.

>> Well I finally found the supplier of the Super Duty Block online. Check it out at: http://www.gtsonline.com/krp/prod1.htm<<

Doug Thompson took over production of the SD block when GM dropped the ball. You should know that the cost is prohibitive at around $2,500 each. They are actually stronger than the original SD block and can accept a variety of cylinder heads. Buying a complete used SD race motor and de-tuning it for street use would be far more economical. Aries pistons makes an aluminum SD block for around $4,000 if you think $2,500 is bad. By comparison, the last new SD iron block I bought from GM cost $850.

>>I wonder if the block, crank, cam and connecting rods will work with stock type pistons and a stock cylinder head?<<

Most parts interchange, but… The SD4 cranks have 2.10 rod journals (SBC). The stock crank is 2.00. If you run a SD crank you need to change the rods. The rod length and crank stroke influence the compression height spec of the piston. If you increase stroke or change rod length, new pistons are required. All SD heads use 1/2 head bolts. All production heads use 11mm. You need to drill and re-tap production blocks if you run a SD head. SD blocks already have 1/2 head bolt holes. SD blocks also have all the stock mounting bosses, so you can bolt up all the stock accessories if you want.

>>I know this sounds like a “halfway” job but my reasoning is simple, use these components with about 9:1 or 10:1 compression, at about 2.7-3.0L, do a mild porting job on the stock head, install lighter valves and stronger valve springs with better rocker arms (rollers maybe).<<

The production “swirl-port” intake ports are restrictive. The first thing you should do is hog out the stock intake ports or use a SD head. The next weak link is the crank. The S10 truck block and 1988 crank with center oil pump drive gear are the strongest stock parts. If you add displacement with a larger stroke SD crank, you are into a SD head to match increased flow requirements. An SD head on a production block is a far better match than a production head on an SD block.

>>I have looked into various options for my engine rebuild. A local machinist I visited, who builds racing motors said that the problem with the Duke is not necessarily the bottom end but the head. It is restricted, thin, and prone to cracking.<<

Yes. They are OK for performance street use if you open up the intake port and check for cracks.

>> So, maybe the way to go for a half and half is to leave the bottom end basically as it is and go for the upper…….<<

The bottom end is good for 150+- HP. Maybe 180 with the right components (88 crank/S10 block). The duty cycle goes down as power output goes up. Don’t expected it to last like a 100 HP production motor.

>>I need facts here, not rumours or speculation. What is the problem with the Iron Duke regarding the 5000rpm ABSOLUTE rev limit I have heard mentioned.<<

It was a low-cost, entry-level power plant for a lot of GM cars, not just Pontiac Fieros. The crank was made as light as possible for throttle response and fuel economy. It was designed for low performance cars and low performance driving. The stock crank is cast and weighs 30-35 lbs. The Super Duty counterpart is forged 4340 and weighs 50 lbs. The SD motors started to blow up at about 9,200 RPM according to Vanderly. These were under controlled dyno room conditions. Don’t know of hard data on production crank limits, but sometimes they flex and cause rod bearing failure before they break. If GM “rated” it at 5,000, it can go higher. Just like the Getrag 5-speed is “rated” at 200 ft lbs torque, but handles more than that. You are cutting into life expectancy when these guidelines are exceeded. GM has warranty concerns in mind when they “rate” parts.

>>Is there an inherent problem with the crank and bearings? The block appears to have five well supported main bearings (even if the main caps are not exactly “beefy”). The connecting rods are reasonably long so they should not suffer from angularity problems. With a good forged crank and good quality connecting rods (tested so as not to be flawed as many of the early ones were) will this engine hold together.<<

There is nothing wrong with the design. It was just optimized for economy and not performance. Of the bazillion 2.5 liter motors made, how many saw performance driving?. If you were GM, how strong would you have made the production crank? A forged crank supports over 200 HP. The problem is that while they are out there, they are near impossible to find these days. Only option is a billet crank from SCAT for $1,800.

>>Are people making to big a deal about this engine being weak because Pontiac ran the SD program to build a racing engine and made the stocker look inadequate or is there real cause for concern.<<

Because it was designed as light as possible on purpose, it runs into performance limits sooner than other motors. The same rules apply to other motors, more power and higher rpm equals stronger components. The SD program came about because GM knew they could not get where they wanted to go modifying production hardware. 150 hp is not a bad goal for four cylinders. How many eight cylinder SBCs do you know of making 300+ HP without upgraded internal components? The difference is there is a sliding scale of performance hardware for the SBC. The Iron Duke is black or white, SD or not.

>> Thank you very much, you have cleared up many of the unanswered questions on the 2.5. If I am reading you correctly, a good 2.5 block with no cracks, properly cleaned up but not overbored, combined with a good stock crank and good quality connecting rods. (I guess an 88 crank will not fit the earlier block, an 84)<<

Yes, the 88 crank will fit. The extra mass of the oil pump drive gear adds strength to the unit, but fits in all blocks. The major dimensions are all the same. Just be sure to use a 84-87 cam with the oil pump drive gear. The 1988 cam has no distributor or oil pump drive gears.

>> A cam designed for better mid range power (2000 to 4000 rpm) a porting job on the stock head (check for cracks first, don’t remove too much material), an exhaust header and a holley intake (if you can find one) or a stock intake with port matching. Combine with a free flow exhaust system and the stock electronics would I be reaching 120hp (with a 5000rpm redline)?<<

Porting the head is most important. In the area under the intake valve in particular. Holly TBI & manifold will not add much. Stock intake manifold/TBI flows enough. You may need a higher pressure fuel pump and adjustable regulator. Use more fuel pressure to adjust for VE improvements in the engine. That saves messing with the ECM fuel maps.

>>Would I have a strong running motor capable of hauling the tall 3.32 ratio four speed at a relaxed highway speed with some power left for passing, and decent reliability?<<

It is harder to get more torque at the same rpm than it is to get more hp at higher rpms. If you want a lugger, then a stroked SD crank may be what you want. 125 HP will work on stock bottom end components in rebuilt condition, but peak HP will be at higher rpm than stock.

>>I was on the MSD ignition website today and found that they have a new super duty billet aluminum distributor. The description mixes Iron Duke with SD. Are distributors interchageable?<<

Nope. It’s a “dumb” system that can’t interface with the variable timing feature of the stock ECM. It’s just has a mag pick-up that matches the standard MSD modules. Nice hardware, but only necessary for higher rpm use. Just upgrade the coil on the stock ignition as the first step. Unless you increase compression ratio or spin higher rpm, the stock system design is fine. Money is better spent elsewhere.

If they were to say it is “compatible”, you should be suspect. Since they say it only works with their module, you pretty much know for sure there is no way it will interface direct.

>>This distributor is designed to be used with their ignition controller (such as the #6). I have seen other cars with aftermarket ignitions. I understand the principle of multiple spark and cylinder effects. Could not get a straight answer about emissions control/ECM/TBI etc…… How does installing one of these affect the computer control of the car?<<

It does not interface directly. See above comments.

I am not a big fan of MSD, but their marine grade stuff may be Ok. My street driven beater car uses the stock system w/upgraded coil. No reliability problems, plus it’s emission legal that way.

I do run a simple Adrenaline CD system on another car rated at 180mJ (mil joules) per spark. If you look into it, that’s a lot of spark energy for a single spark system. The mJ spec is most important, but often never published by ignition peddlers… I wonder why?? Racer Wholesale used to sell these systems a few years ago. The Adrenaline brand was nice stuff with mil-spec components, but I don’t think they sell direct under their own name anymore. The trend is to get rid of the distributor, get rid of the spark plug cables, and now to focus on a better spark event. For a peek into the future of automotive ignition systems, check out the Adrenaline web page. Probably a few more years before these new systems become cost effective and a mass marketer picks up the design.

A 2.5 liter, 3 inch stroke 1988 production crank (left) next to a 3.0 liter, 3.625 stroke SD crank (right) so you can see the significant differences.

Variations of the 2.5L ohv GM four cylinder engine.

There are several variations on the 2.5L engine used in GM models. Before using a non-Fiero block as an engine replacement check out the following list.

Stay away from the oddball FWD only VIN U motor, too many parts are different compared to all other 2.5 motors. It was used only in FWD N-cars, Grand Am, Calais, etc. Crank thrust bearing and cylinder head bolt pattern are a few (see below). The VIN R (Fiero included) motors were used in both larger FWD cars (X and A body cars) and RWD applications with no special mods.

The S-10 truck block is good because it has solid main webs like the SD block. It is cast from average grade iron though, where as, the SD block uses 40,000 psi high nickel iron. The SD blocks come drilled for a starter mount on both sides.

The Vin E 2.5 liter truck motor was used in both Astro/Safari vans and the S-10/S-15 trucks. I think the later model 1991+ VIN A was only used in the pick-up trucks. The pick-up trucks have the starter on the right and the vans have it on the left (fiero side). Starter location can be changed

Here are some general VIN notes regarding the various 2.5 liter motors:

Vin V 1977-1980 Carb non cross-flow head (intake & exhaust manifold on same side)
Vin 1 1978-1979 Carb non cross-flow head
Vin 9 1979 Carb non cross-flow head
Vin F 1980-1983 Carb export only
Vin 5 1982-1983 Carb cross-flow heads from 1982 on
Vin 2 1982-1986 TBI Thrust brg length 1.009, Head bolt spacing 3.75
Vin R 1982-1992 TBI FWD/RWD/Fiero Thrust brg length 1.009, Head bolt spacing 3.75
Vin U 1985-1991 TBI N-car FWD Only Thrust brg length 0.940, Head bolt spacing 3.67
Vin E 1985-1991 TBI S-10, Astro Van Thrust brg length 1.009, Head bolt spacing 3.75
Vin A 1991-1993 TBI S-10 Thrust brg length 1.009, Head bolt spacing 3.75

The VIN E and A truck motors were also used in postal vehicles. That’s right, the mailman has a better block than you do

SEEK ADVICE FROM ONE WHO KNOWS HOW TO CURE A FAILING FIERO

POWER SECRETS FOR THE 4 CYLINDER FIERO

by S. J. Wynman

Most Fiero owners have 4 cylinder engines to power their cars. It appears no one has ever cared to have any real performance enhancement for these Fieros – well, your time has come! Now you can read about some methods to improve the overall engine performance of the stock Fiero 4 cylinder motor. This article is divided up into several topics:

1. Throttle body enhancements
2. Port Matching
3. Octane Tuning
4. Decarbonizing
5. Valve Guide Sealing
6. Increasing the Redline
7. Harmonic Balancer usage
8. Performance Build Up Parts List

Not all of the recommendations will apply to every year 4 cylinder Fiero. The first thing you must realize are the differences between the various 4 cylinder motors GM installed in the Fiero. The Table below summarizes the differences as they pertain to the article:

THROTTLE BODY ENHANCEMENTS
Back in the mid-1980’s HOLLEY felt they had a quick answer to the lack luster performance offered in all GM 2.5 Liter motors. They actually hit on something good, but it appears the idea was not an original one. GM used a performance Throttle Body Injection (TBI) unit on one of the original 1984 INDY Pace cars. GM later provided HOLLEY one of the prototype units and HOLLEY mass-produced them. Not only was the throttle body bore increased from 1.68″ to 2.00″, but the single injector output was increased to make use of the increased air flow. Although the result was impressive, HOLLEY wanted even more. They developed their own intake manifold, which had a larger intake runners, and TBI mounting bore to accommodate the larger throttle body bore. As a result, the combination proved to be excellent. This TBI can even bolt onto the stock 1984 through 1986 intake manifold. HOLLEY provides an adaptor gasket to allow the new TBI to bolt onto the old manifold. A few years ago HOLLEY discontinued their intake manifold, but you can still realize many of the HOLLEY intake manifold benefits. What you should do is machine out the opening in your present intake manifold. Do not open it up to the full two inches as this will probably interfere with the existing EGR passages. Use your judgement as to how much material can be removed. You can use the 2″ HOLLEY gasket as a guide. Scribe this diameter onto the intake manifold. Stuff the intake hole with moist rags to help catch the aluminum which is being removed from the intake manifold.

If you own a 1987/88 Fiero, you will need to fabricate an adaptor plate. GM totally changed the design of the TBI and intake manifold. You cannot use an earlier design intake manifold as the head on the 1987/88 has also changed. The earlier intakes will not bolt up to the newer head. All this means that a simple adaptor plate will have to be fabricated allowing the old bolt pattern of the HOLLEY TBI to be mounted onto the new GM designed intake manifold. Use a 1/4″ aluminum plate along with a new 1987/88 TBI intake gasket. Angled screws must be used to maintain a low adaptor plate height. Remember, you must still open up the TBI bore on your intake manifold. If you are lucky enough to find one, use a HOLLEY intake manifold (except on 1987-88).

PORT MATCHING
As a simplistc example, an engine can be seen as an air pump. The more air the engine pumps. the more power it develops. In order to increase air flow, any obstructions must be removed the air flow path. The first and most obvious obstruction in the 4 cylinder Fiero is in the exhaust system. When the muffler and catalytic converter are replaced with high flow units, and perhaps headers are installed (although they are not really a big advantage here), it is time to look at the intake system. The easiest improvement is to replace the air filter with a K&N Air Filter. The next step was previously discussed in the topic entitled Throttle Body Enhancements.

Once this has been completed, it is time to go inside the engine. This brings us to another 2.5 Liter engine improvement which is to perform port matching. The only safe way to perform this improvement is to remove the intake manifold, exhaust manifolds, and the head from the Fiero. Otherwise, dirt and metal particles will enter the cylinders and drastically shorten the life of the engine.

This is a process where the gasket, between the intake manifold and the head, are used as a template for both the intake manifold and the intake ports on the head. There is enough metal on the desired work surfaces so the port matching can be accomplished safely. The head should be off the engine and all of the valve train should be removed. After the work is completed, the heads should be thoroughly rinsed and cleaned. Follow the GM or Haynes shop manual for the removal of these components.

HEADS. The intake ports are first painted with a blue dye. The intake to the head gasket is then laid on the heads intake side using a manifold bolt as an alignment device. Use an Exacto knife to scribe the intake passages of the gasket onto the head. You will notice the port openings of the gasket are larger than the intake port opening of the head. Now use a 3/8″ flame shaped carbide rotary file installed in a die grinder (capable of 20,000+ RPM speeds) to expand the intake passages of the head. Only enter the head by 1″. Going beyond this point may result in head, valve, or valve guide damage unless you have previous experience in the porting and polishing process. Use your fingers as a guide to determine how the work is progressing. The newly improved openings should have a smooth transition into the head.

The exhaust side of the heads can use the same improvement. The exhaust side will require substantially less work because the ports are closer in size to the exhaust manifold gasket ports. Use the technique above to port match the exhaust ports.

INTAKE MANIFOLD. The same gaskets used to improve the intake ports on the head are now used to open up the intake manifold to head ports. This is the most restrictive area in the intake tract. Make sure the holes are open and clean. Use brake cleaner and Gum Out to clean the passages.

Later, when installing the intake manifold, use FELPRO BLUE as a gasket sealant on both sides of the gaskets and follow the shop manual torque sequence for tightening the intake to head bolts.

The intake manifold was factory painted with a silver paint on most 4 cylinder Fieros.

EXHAUST MANIFOLDS. The exhaust manifold is made of tubular stainless steel. The manifold is basically a four into one header. Believe it or not, this manifold is relatively free flowing. Concentrate your efforts in the area where the “header” connects to the rest of the exhaust. Do not remove more than the obstructions, as the manifolds are relatively thin walled. Also, do not trim or port match the mounting flange of the ports themselves, as this is where the welds are, which hold the mounting flanges onto the stainless steel pipe. You will end up cutting through the welds which hold the stainless steel tubing to the mounting flanges. Clean out all of the metal particles, otherwise they will end up either in your engine or in the catalytic converter.

The exhaust manifold was not factory painted.

OCTANE TUNING
One of the gasolines octane rating characteristics is its resistance to pre-ignition. The higher the octane, the higher the resistance to pre-ignition. As an example, 93 octane gasoline is more resistant to pre-ignition than 87 octane gasoline.

To a limit and as a basic rule of thumb, the more your engine timing is advanced, the more power it will make. The two draw backs to this theory are that more advanced ignition timing settings will tend to promote pre-ignition and also increase exhaust emissions.

The secret here is to use high octane gasoline at all times. Once you have purged the lower octane gas from your tank, by constantly diluting it with higher octane gasoline, you can reset the timing of your Fiero. This trick is limited to 1984 through 1986 2.5 Liter motors as the timing is totally ECM controlled on the 1987/88 4 cylinder Fieros. You should follow the Fiero shop manual for the details of this procedure, however the following are abbreviated steps on how to perform this task. This is done with a timing light and 13 mm socket. Run the engine warm and then loosen the distributor. Move the distributor to increase initial base timing. The normal base timing is 8 degrees BTDC. Now advance the timing to 10 or 11 degrees BTDC and tighten up the distributor. By doing this you are resetting the initial timing of the engine. The ECM cannot determine the base timing and assumes you have set the initial timing to 8 degrees BTDC The ECM now adds its own calculated advance curve to this new base timing. This means the 10 or 11 degree advance you have set will remain in place throughout the entire RPM range.

Now you have must test the new timing settings. In 95% of the cases the new timing will not be a problem. For the other 5%, the problem is with the motor. High carbon deposits and poor quality gasolines are just two examples. With the side windows open, accelerate and listen for a rattling or knocking noise. Hopefully you will not hear either sound, meaning everything is alright. However, if you hear these sounds, back off the timing by 1 degree and repeat the test. Repeat this step until no strange noises are heard.

The advantages you will experience by completing this task are more power and better fuel economy. The down side are increased exhaust emissions. This is the reason why GM limited the Fieros 2.5 Liter timing to B degrees BTDC. It is for this reason you should advance the timing only if your Fiero is to be used in off road applications.

DECARBONIZING
Carbon deposits have always been a fact of life with the internal combustion engine. Unfortunately, the introduction of fuel injected engines during the mid 1960’s had introduced a new set of problems. The problems included new areas of carbon deposits. Carbon deposits accumulate everywhere in your engine. The only way to slow down this process is to use premium name brand gasoline. According to a spokesman from MOBIL, a detergent with anti-carbon properties is placed in all grades of gasoline sold by MOBIL. The only difference is the concentration of this detergent varies with the grade of gasoline. The premium grades contain the highest levels of the detergent additive.

Carbon deposits form in quantity in two areas of the 2.5 Liter Fiero engine, the intake tract and around the intake valves.

The intake tract can be completely clean only through disassembly and the use of a wire brush. Aside from doing this you can clean another area, which immediately affects performance, and is accessible with the engine fully assembled and also still being in the Fiero. The others are in the throttle body. Excessive carbon can prevent the throttle plates from closing completely or even blocking some of the vacuum passages. The throttle plate can become stuck (open or closed) and even end up setting some ECM codes. The air cleaner side is always nice and clean. As soon as you pull on the throttle cable to open the throttle plate everything is black. It is this black carbon which you must clean. This is accomplished with a brass tooth brush and several cans of Gum Out Carburetor Cleaner. First place a small clean damp rag just past the throttle plates. This will prevent debris and excessive amounts of Gum Out from entering the engine. Soak the blackened area with Gum Out and then use the brass brush to loosen it. Remove the debris with a clean rag. Spend extra time cleaning behind the throttle plate, the throttle plate pivots, and the throttle body bore area where the throttle plate touches.

Carbon around the intake valves is a much more severe and difficult problem to correct. The problem arises when the cool gasoline leaves the fuel injector and hits the heated valve causing some microscopic deposits to be left behind. This problem is further compounded when the intake valve guide seals (two per intake valve, an Umbrella type and the standard “0″ Ring type) deteriorates which allows oil to build up on the valves, which can amount to an incredible build up. This can actually block most of the air flow into the cylinders. This results in a choked engine which refuses to perform. Some companies sell products which claim to remove this carbon build up, but I have not experienced ant to perform as claimed. The only efficient way to remove this intake valve carbon build up is to remove the intake valves from the heads and either replace them, or clean them with a sharp chisel and a wire wheel. This procedure requires removing the heads from the Fiero.

VALVE GUIDE SEALING
Virtually all engines contain valve guide seals. The purpose of the seals are to prevent oil from entering the valve bowl area and either getting burned (intake) or leaving as a cloud of smoke (exhaust). Heat and time take their toll on the seals. The result is carbon depositing on the intake valves developing quicker (see above), resulting in the Fiero smoking after sitting still for sometime.

The valve guide seals can be replaced without removing the heads from the engine. As a quick overview the following must be performed. Follow the shop manual for detailed procedures on each of the following over viewed steps:

1. Remove the valve covers
2. Remove all four spark plugs
3. Remove all eight rocker arms
4. Install a compressed air adaptor into the spark plug hole and apply compressed air. This will hold up both intake and exhaust valves for the cylinder being worked on.
5. Using one of the rocker arm retaining nuts, and a lever type on-car spring compressor, depress the top of the valve retainer, With needle nose pliers remove the two valve stem keys (keepers). Release pressure on the valve spring, then remove the retainer and valve spring. The compressed air will hold up the valve, Remove the old “0″ Ring seal (both the intake and exhaust valve have this seal), and wiper seal if you are working on the intake valve, Install the new seal(s) and reverse the process to replace the valve keys.
6. Repeat steps (4) and (5) above for the other 7 valves.
7. Re-assemble the remaining components of the motor per the shop manual.

INCREASING THE EFFECTIVE REDLINE
The redline, or maximum operating RPM of the 2.5 Liter engine is 5000 RPM. Most stock four cylinder engines have a hard time finding the high side of 4000 RPM. Many engine parts can limit the maximum RPM of an engine.

A large step can be realized in achieving that 5000 RPM redline in the 1984 through 1986 Fieros. This is done by replacing the ignition coil. GM makes some nice ignition parts, but fell short with the coil. The answer: Bolt on an ACCEL, or other brand of high performance coil onto the rear trunk sheet metal, near the original stock coil location. With a coil change, a free flowing catalytic convertor, and a new TBI alone, you will really wake up the little motor.

HARMONIC BALANCER USAGE
A harmonic balancer absorbs the torsion vibrations which occur within the crank shaft. These vibrations are caused as each cylinder fires and part of that “power pulse” is sent to the crank shaft, in a direction which does not contribute to the power being output to the flywheel. Having a harmonic balancer does not eliminate the pulses, but it does give them a place to go. This will contribute to longer crank shaft and timing gear life. GM introduced a harmonic balancer for the 1987/88 Fiero 2.5 Liter motor. The part number is 10101369. Unfortunately, GM did not think about the earlier Fieros models.

BUILDING UP THE FIERO 2.5 LITER MOTOR
GM developed a nice 2.5 Liter engine program. This program is called the Super Duty Four Cylinder. Once this motor is built up correctly, it will give a 1996 Corvette a run for its money. The bad news is that just about every piece of this motor is race ready, and very expensive. A completely assembled motor will run about $7000.00. As you can see, this is a little on the high side. Do not give up hope or even your stock four cylinder. if you follow all of the previous suggestions, your stock 2.5 Liter will be good for about 110 to 115 HP. Considering the stock motor puts out about 94 HP this is not too bad. If you want more, then a complete rebuild is necessary. Standard Blueprinting practices are recommended, along with the following parts:

1. Pistons – TRW piston part number 248SF-SO, TRW ring part number is T8370-30. This is a forged 0.030 oversized piston. I do not recommend an over bore larger then this as the block is not to strong or thick in the cylinder area. Make sure a deck plate is used when boring and honing the cylinders. The compression ration will increase to about 9.1:1 where stock is approximately 8.4:1. I strongly recommend the use of the previously described improvements if you decide on these pistons. These pistons will fit in the 1984 through 1988 motors.
2. CAM Shaft – TRW TP-209, Intake Lift = 0.409″, Exhaust lift = 0.516, Duration lIE = 204~/2 140. This is a nice improvement over stock and which will not require head work for the spring perches. The stock ECM will also work with this cam shaft. I strongly recommend the use of the previously described improvements if you decide on this cam shaft. This cam is a direct bolt in for the 1984/85 motor. You can use it in the 1986 to 1988 motors if you use conventional lifters in place of the roller lifters. You will also have to use the 1984/85 push rods in the later motors if you use this cam shaft.
3. Timing Gears – Cloyes makes a nice all steel set. GM has improved their own timing gears which can be ordered under part number 10101790. This gear set will fit the 1984 through 1988 motors.
4. Valve Springs – TRW part number VS1 100, using retainers SR363. These parts can be used only in the 1984/85 motor. Use the stock springs with the 1986/88 motor.
5. Oil Pump – TRW High Volume part number 50132. This oil pump can only be used only in the 1984 to 1986 motors. The 1987/88 motors use a gyrator type pump which is part of the balancer assembly.
6. Use brand new GM Head, Connecting Rod, and Main Bearing Cap Bolts. Follow the latest Torque-to-Yield Bolt specifications.
7. Replace the catalytic convertor with a high flow ACCEL unit.
8. If the oxygen sensor is 2 years old or older, it should be replaced. The accuracy decreases the range of forcing the engine to run lean.

Balance the reciprocating crank shaft mass to within + 0.5 gram. This includes the crank shaft, pistons, rods, rings, bearings, front hub, and flywheel. This will remove much of the engine vibration characteristics and provide a slight increase in power.

Increase the fuel pressure on the HOLLEY TBI unit (it is adjustable) to 15 pounds.

After the stock or aftermarket header, replace the stock exhaust with a 2 1/4″ stainless steel unit such as the one sold by the Fiero Store. This removes the stock restrictive muffler and replaces it with resonator tips. The sound is a little louder, but it does sound nice.

This is about as good as you can expect with the stock block, crank, and head. You can expect the engine to produce 120 to 130 HP if all of these modifications are made.

We can debate this until the cows come home….. but unless you go the SD route you ain’t gonna make a significant difference in the overall performance of street driven Dukes with add-ons (been there – done that). If you are successful in cranking out significantly more HP, the lower end will not last much longer. Experience has taught me (and others) that when you start consistently pushing a Duke over 5,000 rpm it is going to self destruct. It ain’t a matter of “If”, it is when. Do you ever wonder why the early 2.5 turbo kits died off so quickly? It wasn’t the introduction of the V6 – they were a prescription for a broken crank or pitched rod.

Still, there are some things you can do to a Duke to improve performance that are simple, cheap, don’t compromise reliability and should be done anyway. Sadly, they are often overlooked or ignored. It has been at least 5-6 years since I put this on the list, but it is still valid. If you have previously done these, GREAT! If not, try it – you’ll like it. (You will also get better gas mileage)

1. Replace the fuel filter. Do this every other oil change or 6,000 miles. Restricted fuel filters lower fuel pressure. Lower fuel pressure translates to a drop in performance. This is often overlooked and is true for the 2.8 as well.
2. If you still have the stock converter, replace it with a new high flow unit. Gains will be noticeable as the original L4 brick catalyst is very restrictive.
3. Drop in a K&N air filter – or at least a new paper one.
4. Pop in a new oxygen sensor
5. Change to synthetic oil
6. On 84-86 Dukes, bolt on a performance coil and a new set of lower resistance plug wires.
7. Install a fresh set of spark plugs – NEVER put Bosch Platinum plugs in a DIS car (87 & 88) If you have not added a higher voltage coil and wires, close the gap .005 less than specified. “Trick” plugs (Splitfire, etc.) are OK, but a waste of money as far as performance gains. A set of new steel electrode AC plugs will do just fine.
8. Bolt up the dual outlet muffler and pipes from a 85-87 V6. There are tons in the junk yard for little or noting. Don’t expect a great performance improvement, even if there is one less chamber in the V6 muffler, but it looks and sounds better.
9. Run maximum allowable air pressure in your tires and avoid those tall fat ones – especially on the back. They can change your effective gearing and reduce HP at the point where the rubber meets the road.
10. Try a 160 or 180 degree thermostat. It may take longer for the car to go into closed loop but Dukes seem to run better in the 180-200 degree water temp range. Add a manual fan switch so you can cut it on at will, don’t wait for the fan temp switch to do it or the water temp will soar even with a low temp thermostat.
11. Be sure no calipers are dragging – especially the rear EM brake.
12. Run a batch of carbon removal and top engine cleaner through (Ed Parks sells this and the stuff really works!).
13. For quicker off-on throttle response, disconnect and plug the vacuum hose to the EGR valve. May have to move to mid grade 89 octane gas for this. Also increases emissions. Will not give more overall HP – only quicker throttle response. On a 2.5 the ECM doesn’t know this has been done. (Note this may cause emmissions problems. I.C.)
14. Give the car a wash and wax, clean cars always run better – you know, less wind drag over a slick surface thing.

If you have not done these low cost items, you will be amazed in how much better your Duke will run. Then, if you gotta learn the hard way (like I did) go ahead and face the wind and pull those bills out of your pocket for your visit to the johnny house…… or you could just donate them to me.

No way (short of the SD-4 – see http://fierozone.com and click on “Blast From the Past” for SD 4 articles) will you get the HP gains you want with the other higher cost add on mods for the L4. Port matching and larger TB’s won’t hurt – but they won’t help much either unless you go the whole nine yards (heads, headers, cam, etc.).

One of the most important things you have to be aware of when trying to improve the performance of the Iron Duke is the well-known fact that it has a weak block. Remember that this engine was designed from the ground up to be as fuel efficient as possible. High performance was never a major design goal of the engine. Therefore, strength and the ability to accommodate higher performance was sacrificed in the name of weight reduction. Low cost was another design goal, so more aggressive steps to increase efficiency such as porting and polishing were overlooked. It is in areas such as these that I believe the performance can be gained; not by pulling more power out of the engine, but rather removing obstructions or restrictions that are consuming the power that the engine already has. I believe that if you are going to be successful, you have to accept the concept of ‘power through efficiency’. Any other approach is going to result in a blown engine. I can almost personally guarantee it.

That said, the next most important thought you should keep in mind is that of properly matching all the parts during the rebuild. An engine with a well-matched set of conservative parts will usually provide better results than an engine full of high performance parts that are not matched. Take a good long look at your driving habits and your expectations for this vehicle. If the car has a manual transmission, what RPM ranges do you normally shift at? What gear do you prefer to use when passing people? What speed are you normally driving at when you decide it’s time to ‘get on it’? Is this a daily commuter or a weekend sportster? Take these thoughts into account before, during and after you start to rebuild the engine.

You also need to be realistic about your expectations. The Iron Duke is a great engine for efficiency and moderate to respectable performance. If you are looking for a truly significant jump in performance, say more that a 25% increase over factory rated HP; this is not your engine. By the time you pull that much HP out of the engine, you will have spent a small fortune and in all likelihood the engine will fail very quickly. This article is for those that have more time and patience than money and just want to have a reliable, efficient, smooth running little 4-banger that gives them reasonable performance when it is occasionally needed. If you are expecting more, go for a V6 or V8 conversion. The bang to buck ratio will be much better with a conversion approach and they are not as expensive as you might think.

If you are an experienced mechanic and are comfortable with choosing your parts, by all means do so. If you are a little foggy in this area, like myself, seek out the advice of an expert in your area. Most of these people are more than happy to share their knowledge with you, especially when they see that you have already given some thought to how you want the engine to perform and considered how your driving habits have played into your decision. If you don’t trust your mechanical skills at all, you can have a local outfit build the engine for you. Just make sure you pick a quality shop to do the work. If you have no fear of spinning wrenches, feel free to ask an expert for guidance on how to best match and assemble the right parts for your needs. They usually don’t mind being used as a resource because they know that you will have to have certain machine work (boring, milling, turning, etc.) done somewhere, and if they are helpful, they just might get your business.

The first step to building an engine is to select a camshaft that matches your performance expectations. This one part more than any other will determine the true nature of your new engine. Again, be realistic. If you try to put a full race cam in, you will have to take extreme measures to take advantage of it, by which time your will likely have exceeded the block’s capabilities. Once you have chosen the camshaft, you should build the rest of the engine around that. This will affect what type and compression of pistons you use; how you have the head milled and what type of valve springs you will use. It can affect what kind of exhaust system you install and what type of ignition products you buy. Based on the camshaft, you might choose to port and polish the head and intake manifold. You may opt for a three or five angle valve job. Of course, some of this may be a bit overboard, and if you choose a cam that HAS to have all of this, you’re probably being a bit aggressive. Again, consider a conversion instead of going overboard.

I was fortunate enough to have an engine designed for roller cams, which made having a new profile ground onto the original cam a viable possibility. Roller cams have far more success than standard tappet cams with longevity after being reground. This was certainly a good thing because there were not many aftermarket options for a new cam at the time. Kams, Inc. in Oklahoma City put a mild RV profile on the cam that adequately matched my driving style. It was certainly streetable; started easily even in winter; had a good mid-range power curve and respectable fuel economy at highway speeds. From there, I chose 9.5:1 compression pistons that would pull a little more power out of the fuel without inducing too much stress on the weak cylinder walls. I had a great local outfit named Buddy Rice do all of the machine work on the engine. They were the ones that helped me choose parts that would perform well with the camshaft profile I had selected. The block and head were both cleaned. Then, I had the centerline bore reestablished on both the camshaft and crankshaft bores. They also trued up the bores on the connecting rods. They milled the head and performed a 5-angle valve job, and then shimmed the valve springs to match them with the camshaft. The crankshaft journals were also turned, along with the mains that were ‘recentered’ to match the work done on the block. They looked at the idea of balancing the crankshaft, but ultimately decided against it because of its light weight and the fact that it was already fairly well balanced. While the engine was still at the shop, we carefully looked over all the parts for any signs of wear. Anything that showed any significant wear was replaced. Better to catch the problem now that to find it later after it fails.

With the block and head prepped, I took all the parts home and started putting the engine together. I didn’t do anything special while assembling the engine. I just made sure I was liberal with the engine assembly lube. I use this stuff on everything, not just the camshaft. I also made sure that I followed the torque specifications for everything; using several increments up to the final torque for anything over 25 ft/lbs. When working on the engine or suspension, I never tighten anything with an ordinary wrench. I always use a torque wrench to make sure I am not overtorquing something. I also do this to make sure that matching bolts on a part are torqued uniformly to prevent warping.

One note of caution; whenever you are not working on the engine, make certain to but a thick plastic trash bag over the engine and seal it airtight with tape. When I first started the engine, I had no oil pressure at all. After taking it back apart, I found that a wasp had built a mud nest in the oil pump that completely blocked the passageway to the oil filter. Fortunately, the liberal use of the assembly lube saved the engine from damage. The bag will also help protect the engine from dust and humidity.

At the time of this writing, this was the extent of the work done to the engine. Notice that the only higher than stock performance parts are a mild camshaft and slightly higher compression pistons. Everything else was just removing any possible sources of resistance, and making sure that each part could do its job in the best possible environment. The engine already performs extremely well. As time permits, I will port and polish a spare head and intake manifold from another engine. I will install them along with a new exhaust, headers, Holley’s Big Bore TBI and a good aftermarket coil. Some additional notes would be that I removed the restrictor plate underneath the TBI in the intake manifold; I use a cooler thermostat and coolant fan switch; and that I disconnected and capped the vacuum line to the EGR valve. If you choose to do the same, make sure you reconnect the EGR for one day every month and take the car for a long drive. That way, it will work when it is time to get your inspection. Something else to keep in mind is that I personally would probably never go this far with another Iron Duke. When I started, I did not know about the ease and tiny cost of certain V6 conversions. Also, I was fortunate enough to have a rare engine. This is a 2.5R engine, not the normal 2.5L. GM ran the numbers on it and describes my engine as an ‘84 Fiero Second Design’ engine. They swear it is definitely for the ‘84 Fiero even though it has roller lifters, which the ’84s are not supposed to have. I’m certain this plays a part in the better performance, and in this case, makes the extra effort worth it. I have a 4 banger that performs very close to many of the V6 Fieros, yet retained the efficiency of the 4 cylinder and did not sacrifice reliability or life in the process. I paid a whopping $200 for the car and spent around $1,000 rebuilding the engine. As long as I take care of it, this little baby will last forever.

The Pontiac Fiero has been available with three differently geared Muncie 4 speeds, an Isuzu 5 speed and the Muncie Getrag 5 speed. The 3 speed model 125 is the automatic transmission (with lock up torque converter). Here is a brief run down of what was available and what it means.

Transmission: Simple working definition, a device for transmitting engine power to the the final drive (and then on to the wheels).

Transmission lore is a mixture of fact and myth. Let us explore some of these points with an eye to the Fiero. (Note: emphasis on issues of importance to potential engine swappers)

Automatics, in the case of the Fiero a TH125 three speed with torque converter lockup. A reliable transmission, if not exactly an exciting one. The automatic is a good choice with V6 models, or sufficiently beefed up for a 3800 or V8 engine swap.

4 Speeds, again the four speeds are an excellent choice for the high torque, low rpm powerplants. A 1984 economy 4 speed (option MY8) would make a very good high speed cruiser with a Chevy V8, allowing decent fuel economy, relaxed cruising (about 2000rpm at 60mph) and plenty of performance because of the flat torque curve of the typical 305 or 350. The 3.65 ratio 4 speed used in the V6 (M17) would also prove a good choice giving better acceleration but a rather busy highway cruise and lower fuel economy, this transmission would be a better choice for a 3800 V6. The 4.10 4 speed (M19) is best left to the drag racers (or as an acceptable but less than ideal unit for the high RPM twin cam engines.). There is no real difference between the 4 and 5 speeds other than the fact that the 5 speed has more intermediate ratios which allows you to keep the engine in its powerband.

That’s it! As a matter of fact when Porsche built their first Turbo 911s they actually replaced their normal 5 speed with a beefed up 4 speed since they could build a very strong 4 speed which would be lighter than an equal 5 speed (Their normal 5 speed was not strong enough). They reasoned correctly that the increased torque of the turbo made the extra ratios unnecessary. Marketing however showed that people saw a 4 speed as being “low tech” so the 5 speed soon returned BUT ONLY BECAUSE PEOPLE WHO KNEW LITTLE ABOUT CARS DEMANDED IT. Just as a 5 speed V8 combination is unnecessary in a Fiero unless you plan on competitive road racing. This does not mean that a 4 speed is preferred over a 5 speed, just that if you have a perfectly good 4 speed you may not NEED a 5 speed unless you are racing.

5 Speeds, The Isuzu 5 speed attached to 85-88 4 cyl Fieros is not a good choice for a high torque swap, it is not strong enough. This transmission may cause problems because of weak cast alloy (pot metal) shift forks, which could break if abused especially at high rpms. Careful shifting can make these transmissions survive since it is the shift forks, and not the gears, which causes the problems. The gearing of the Isuzu transmissions seems to be a better compromise than the Getrags, but the reliability issue can cause some concern. This leaves the Getrag, although not perfect it is probably the best transmission used in the Fiero. It is strong enough for the high torque V8s and V6s but with the better ratio spread necessary for the cammier engines such as the 3.4 twin cam V6, the Quad Four and some V8s tuned for top end power. If you have one this is the transmission to use for any swap.

Now you may ask what is the point of this little discussion. Simple, many of you may be contemplating a V8 swap but are concerned about the added cost and complexity of finding and installing a Getrag. If you have a V6 with 4 speed, or an 84 with the economy ratios, you don’t need the Getrag. Also decent 4 speeds are available for much less than the typical Getrag ( All Citations with manual transmissions used this 4 speed, but with different combinations of ratios, such as the 2.5 with 3.32 final drive but 0.81 4th gear). In an extreme case, the 6 speeds Chevy sells in the Camaro and Corvette are mainly meant to allow tall gearing for good fuel economy and as a marketing gimick (no flame please, I would love to own one I just want to point out that a 9000rpm Honda VTEC engine would need that transmission, a 6000rpm 5.7 litre V8 does not). With big torquey engines 4 speeds are fine. Now the Iron duke 2.5 like mine, it could use all the help it can get, but since I drive an 84 I have the four speed.

The moral of the story is, if your perfect Fiero must have a V8 than a 4 speed is fine, but if you long for the high pitched scream of an engine on the far side of 6000rpm the 5 speed is the logical choice. The wide ratios of the economy box in my 1984 suits my slow revving iron duke just fine.

Note: All indications are that NO V6 ever left the factory with the 4.10 ratio 4 speed, it was a 1984 only option.

Automatic Transmission Final Drive Ratios:

84-86 L4 had 3.18 final drive.
85-86 V6 had 3.06 (86, at least the GT haven’t seen any in SE had 3.33 optional)
87-88 L4 had 2.84
87-88 V6 had 3.33 (2.84 optional)

All will interchange

Notice! It is a violation of U.S. Federal law to remove, modify or disable emission control devices. Some states, like California, have laws above and beyond Federal regulations.
Fiero has very little in the way of emission control hardware. There is only the catalytic converter, EGR valve and a fuel vapor recovery canister. None of which require rocket science to fix. (In California nearly all parts of the engine are regulated. Make sure any aftermarket parts you install meet CARB requirements.) There’s also the PCV system. Almost forgot that one.

Catalytic Converter

The catalyst is used to burn off excess fuel and oil that escapes normal combustion. The catalyst usually fails in one of 2 ways. It either disintegrates or gets plugged up with soot. In extreme cases the guts can melt. (Usually if it disintegrates it blocks up the exit port.) The catalyst needs to be replaced when it fails. You can’t fix it.
You want to know which way it failed. If it fell apart then you can likely just replace it but if it’s blocked up with carbon or melted then try to find out why before you install a new one. If the motor is running rich, burning oil, or leaking coolant then these problems must be fixed before the new catalyst is installed otherwise you’ll wreck the new one in short order.
A quick way to test the catalyst is to measure backpressure at the O2 sensor port. According the June 2001 issue of Motor…
With the engine idling, the pressure will usually be below 1 psi on a good system.
Backpressure reading over 1.5 psi is cause for concern. Next, bring the rpm to 2000 and check the pressure again. A good system will usually show less than 2 psi. If the pressure is over 3 psi, the catalyst is most likely going south.
Of course most people don’t have the fancy commercial one of these lying around, but they can be made. You’ll want to use some metal or high temperature flexible tubing to keep the gauge away from the worst heat. You also want a gauge made for low pressure, something with a 5-10psi top end.
You can use an old O2 sensor or spark plug to fabricate the exhaust fitting.
If the catalyst croaks… Once the catalyst is off make sure it hasn’t blown its cookies down the exhaust pipe. With Fiero’s exhaust setup, you can probably suck the stuff back out of the muffler with a shop vac. (Empty the vacuum before starting so you can tell what came out of the exhaust.) If you don’t check for this you could fry the new catalyst. At the very least the exhaust will still be restricted and likely hurt performance.
Many people think the catalyst does nothing but rob performance. Once upon a time this may have been true but today’s high flow catalyst units present very little restriction of exhaust flow. In the vast majority of cases you gain nearly the same performance increase with a new catalyst as having a straight pipe.
·     A straight pipe may give a HP increase but can reduce low-end torque in many engines.
· A straight pipe on an engine with backpressure EGR may also cause odd problems. These engines must have some backpressure to operate properly.
It is illegal in some places to put used catalysts in the trash. Even when it isn’t illegal try to dispose of it at a muffler repair shop or some other place that will send them to be recycled. (They recycle both the metal and the catalyst material.)

EGR

Note! An altered or defective exhaust system can screw up operation of the EGR valve on the L4. How much depends on the specific alteration or defect.
The EGR, Exhaust Gas Recirculation, valve is used to limit emissions and to prevent engine knock. On V6 the valve is ECM controlled but on the L4 it is operated by a combination of engine vacuum and exhaust back pressure.
There’s not much to go wrong with the valve. It can jam or leak which is usually caused by carbon and rust in the valve base. The diaphragm that moves the valve can deteriorate and leak. That’s about it. (In one odd case, I had the return spring or something in the vacuum chamber broke.)
You have to watch that the valve is connected to the right vacuum source. That information is on the VECI, Vehicle Emission Control Information, label on the deck lid. Hooking it up wrong can make it open at the wrong time or not at all.
The main problems with this valve on the V6 are that the valve plumbing likes to crack and the ECM control solenoid likes to get trash in it. The cracks of course hurt engine performance, if the car even runs with these vacuum leaks.
The control solenoid can sometimes be cleaned but you have to watch what you clean it with. You want a plastic friendly solvent that leaves no residue or lubricant behind to collect more dirt.
If you suspect EGR valve problems, take it off and inspect it. The gasket for the L4 valve is only about $1.00. I imagine the V6 one is about the same. (FelPro gaskets…) Always install a new gasket if you remove the EGR. A small exhaust or vacuum leak can cause major hair pulling…
Carbon or corrosion on the valve can hang the valve open or shut. You may be able to clean carbon off with EFI system or Carburetor cleaner. Corrosion will usually mean valve replacement.
Shake the valve. Noise is bad… Nothing in it should rattle.
Push the diaphragm up. You may have to carefully use a tool of some type. (A stick of Plastic or Wood is probably safer than metal.) Does it move smoothly and return to the closed position by itself? If not the valve probably needs replacement.

When does EGR open?

That depends on the EGR in question. I can tell you when it should definitely NOT open. It should not be open at idle or at WOT. Otherwise… On the ECM controlled ones it will open whenever the ECM is programmed to open it.
On backpressure ones, like the Fiero stock 4 cyl, it will open at certain combinations of vacuum and exhaust pressure. Exactly when those conditions will be met is hard to say. It will vary based on the condition and configuration of your car and you driving habits.

Service Warning!

THIS APPLIES TO ALL VEHICLES FITTED WITH THE UNIVERSAL EGR VALVES.
Many replacement EGR valves are of the universal type and come with metering washers that are affixed to the valve prior to installation on the car.
These washers MUST be staked in place. Do not depend on the gasket to hold them. If the washer comes loose it will screw up the metering allowing more exhaust gas flow than it’s supposed to. The washer could even fall into the motor and cause major damage.
To stake them down place a punch or the corner of a chisel in the base of the EGR valve next to the washer seat. Hit the punch to dent the valve base and force metal toward the washer. Do this in at least 3 locations around the washer.
Record the number of the original valve to both the sticker included with the valve and a permanent location on the vehicle or in some other place you can find it again. The label often fades. You’ll need the number if you ever have to replace it again.
To select the correct washer you need the code stamped into the OE EGR shell…

Fuel Vapor Canister

The Fuel Vapor can is a little confusing for many people. It is simply a can of charcoal with a vacuum controlled air vent stuck on it. The emission control purpose of the canister is of course to prevent fuel vapor from leaving the gas tank but it also saves you money if it works right. Fuel that evaporates from your tank costs money and gives nothing in return. The canister catches this fuel and lets the car use it. It’s a small amount at any one time but over the life of a car it can really add up especially in hot climates. A canister that is working right will not hurt performance and will add ever so slightly to your MPG.
The Canister Purge uses two vacuum lines. The large one goes to manifold vacuum and carries the fuel vapor into the engine to be burned. The small one is the control line and goes to a port on the throttle body that opens upstream of the throttle butterfly. When the throttle opens beyond a certain range the purge control valve opens and allows manifold vacuum to draw the vapor from the can.
The only maintenance the canister needs is periodic checking of the vacuum lines and filter. There is a floss filter on the bottom to trap large dirt from entering the can and plugging it up. That filter needs to be kept clear of major trash and should be replaced once in awhile or when damaged. (The filter costs
about a dollar at Wal-Mart.)
There are only a couple things that can go wrong with the canister. It can be damaged by cracking the thing or by over filling the gas tank. “Topping off” the gas tank can force fuel up the vent line into the can and ruin it. While the fuel pump nozzle is supposed to shut off when the tank is full, they are often bad and can pressurize the fuel tank enough to force fuel up the vent. Certain types of “Vapor Recovery” nozzles are great for this.
The purge control valve can fail or its line can be connected to the engine wrong. Either can cause problems. The routing of these lines is also on the VECI label.
The fastest way to test for drivability problems caused by the vapor can is to disconnect and block both vacuum lines. If the problem stops, the vapor can is bad.

How does the canister work?

This explanation is based on an article from Motor Magazine or Motor Age that I can’t find anymore…
The canister is filled with high-grade charcoal similar to a gas mask. When fuel vapors expand out of the fuel tank, they cling to the surface of the charcoal.
The important thing here is that fumes don’t soak into the charcoal grains like most people think. This “small” fact is what makes the whole canister possible.
When the canister is purged fresh air is sucked thru the canister, which knocks the fuel molecules off the charcoal and caries them into the engine. Canister purge in older cars, including Fiero, is usually controlled by a ported vacuum signal from the carburetor or throttle body. In many newer vehicles the canister purge is controlled by the ECM/PCM.
If liquid fuel gets into the canister it will soak into the charcoal just like lighter fluid does in your grill. Once that happens the charcoal is ruined. Even if you could dry out the liquid fuel, the carbon won’t recover.

PCV system

The Positive Crankcase Ventilation system is both an emission control and a significant improvement to engine longevity. The job of the PCV system is to remove fumes from the crankcase and burn them. These fumes pollute the air and if not extracted from the engine they promote contamination of the oil and varnish on internal parts.
There are 2 major parts in the system, an air filter, and the PCV valve. Make sure both are clean and that the vacuum line(s) and vent hose are sealed.
The PCV valve should be replaced every couple years at most. There is a spring in the valve that is critical to proper operation. The spring will weaken over time. A bad PCV valve is hard to detect. The obvious test of shaking it only tells you it’s not stuck closed. It won’t tell you the spring is weak.
Make sure you clamp all the joints in the PCV line. The rubber parts can’t be trusted to seal themselves. Don’t over tighten the clamps or you will damage the soft parts.

Emissions Service Parts

Note: Be careful buying PCV parts for the 87-88 4 cylinder motors! Many parts books incorrectly list them as using the same parts as the older 4 cylinder engines. Double-check them against Grand Am or Olds Cutlass Calais of the same years.
I had a heck of a time finding the correct PCV filter for my DIS motor until I looked it up under the Olds line. I’ve noticed some parts catalogs also list ignition parts wrong as well.
This is a quick list of stuff I’ve seen listed and where. I’ve seen AC Delco emissions parts for DIS 4 at Parts America. I imagine they cover other years but I didn’t feel like checking them all. (I think the same vapor can is used in all Fiero.)
The part numbers for the DIS motor parts…

As far as I can tell, the AC EGR is an OE matched unit. (At least that’s the picture they have on their web site.)
GM Parts Direct lists the Vapor Canister for about $25. (Use GM # 17075840)
They don’t have the EGR valve.
No AC Delco part was listed for the one V6 I looked up. (86 GT) Because the V6 valve is ECM controlled it’s not as critical who made it as long as the new part is high quality and provides the correct gas volume.
If you can’t find a stamping number to use for universal EGR’s, try using the information listed with Niehoff Ignition’s parts. Here’s the info they list on Parts America for an 86 GT with their part # FE134A valve. (I’ve never use Niehoff stuff but there catalog info is handy. They are the only one I’ve seen so far that lists data like this.)
[E. G. R. Valve] OE Number 17085897; Orifice Number 11; Use EGR Valve Gasket {FE302}; Use EGR Tube Gasket {FE354}
Notice the OE stamping number above. You could use that bit of info for any universal EGR. (The one you have may use the same metering washer or a different one. Get that info from the chart that comes with the new EGR.)
The V6 EGR solenoid I found listed under “Vacuum Regulator Valve” in the Fuel Injection parts. Parts America says it usually ships in 5 business days.
AC DELCO 214-361 $102.99 [EGR Vacuum Regulator Solenoid Valve] GT, SE Listing
Everyone who’s got them likes Rodney Dickman’s catalyst kit. It has the needed stainless steel adaptors needed for installation.

4 cylinder motor mount

There are 2 kinds of motor mount available for Fiero 4 cylinder. (I think this applies to all of them…) You can get them solid or liquid filled. The solid is a little less expensive but the liquid filled is better at isolating vibration. Of the two, I prefer the liquid filled even if it’s a bit less durable than solid. Anything that reduces engine vibration traveling to the car body is a good thing. (The liquid mount is usually the easier one to find in stock.)

How do you detect a bad liquid filled mount?

In the drawing above I’ve colored the steel body of the mount green. Notice how the rubber passes over the safety pin. The motor bracket can touch the rubber over the pin but mustn’t compress it any significant amount. If the motor bracket is resting against the metal body or the safety pin then the mount is bad and must be replaced.
Note! It is entirely possible to get a new mount that is bad! When you buy a liquid filled mount, you should not hear allot of sloshing when you shake it. If it sloshes, it’s bad. Don’t accept it! (The mount will usually have a tiny air bubble in it but it shouldn’t slosh like a half empty soda bottle.)
A sloshing mount has air in it and won’t be able to support the motor. Once installed it should pass the above inspection, if not then take is back and get another.

Changing the Mount

You need a 15mm socket and a 15mm box end or flair fitting wrench. (I prefer the flair wrench. It seems to grip better.)
Disconnect the battery.
Disconnect one end of the torque strut. (Dog Bone)
Jack the car, install a jack stand, and remove the right rear wheel. The top nuts are easier to get if the wheel is off. (Yes, I’ve tried both ways… take the wheel off.)
Remove all four nuts from the mount. These are lock nuts and will need to be turned with a wrench all the way off.
Jack the motor up. Use a block of wood between the jack and oil pan. (If you don’t use the block the oil pan could collapse.) Keep the jack over toward the transmission to it will lift straight.
Pull out the old mount and clean the motor bracket. Don’t loose the top washers that are likely buried in crud.
The new mount only fits one way.
Put the heat shield, the nuts and washers back on.

Mount care

If you have a 4 cylinder using traditional spin on oil filters… (This isn’t an issue for filter in pan motors.)
When changing the oil, stuff a rag into the engine bracket to catch oil that runs down while you change the filter. If you can keep oil off the mount then it will last longer.
Consider making a shield for the mount out of some aluminum sheet and sandwich it between the top of the mount and bracket. This will help keep oil that runs down the bracket from pooling on top of the mount. Constant soaking in oil will shorten the life of the mount. It doesn’t matter much how you make it as long as it deflects the oil that invariably spills from the filters during changing.

Transmission and V6 Motor Mounts

These are solid rubber mounts and there’s not much to them. Most of the time you can easily see damage to a bad one. Sometimes the mounts tear away from the metal parts too cleanly to be obvious. If you think a mount may be bad and you can’t see damage, try gently jacking up whatever the mount supports.
Jacking will spread open any tears in the rubber. Don’t get rough with the jack or you could tear a good mount.
When ever you have to replace a mount make sure you loosen all the others.
That way the mounts can all settle into position without loading.
Except for 86.5 and later 4 cylinders with automatic transmission, you’ll almost never see just one mount that is bad. The front mounts and the dog bone are the most likely to fail but it’s entirely possible for all of them to be bad. (The 86.5 and later 4 cylinder/AT setup only has one engine mount and one transmission mount. Read the torque strut article for more info…)
Oil soaked mounts may not be torn but are probably considerably softer than they should be. Oil and other chemicals break down the rubber over time.
Always clean off any oil that spills on them.

Polyurethane mounts

Polly mounts are generally perceived as better than OE style vulcanized rubber mounts. In some applications they probably are but for general use they simply aren’t needed and are unlikely to do anything performance wise for the car.
Depending on just what ones you buy, many OE style mounts are stronger than the ones that came with the car.
Polly can also pass more vibration to the car, especially at idle in automatic transmission cars. (This has been proven with polly dog bones. The 4 cylinder motors are the worst for this.)
Polly mounts can add some color to the engine bay. They may tolerate the heat better.
They are more resistant to oil grease and other chemicals, which shouldn’t be much of an issue. The mounts shouldn’t be getting allot of stuff on them in normal use. The main source of oil on mounts is usually a sloppy oil change or a leaking gasket. Rubber mounts usually last years in even the worst environments.

While this article was originally written for Fiero 1987-88 L4, it applies to all vehicles with self tensioning serpent belt systems.
WARNING: Do not assume that the belt listed in the catalog fits your engine! If the belt forces the tension assembly out of range you can and likely will break things.
WARNING: NEVER force the tension assembly! If you don’t break it instantly, it probably won’t last long. Most tension assemblies have internal stops. IF the tension assembly is actually binding, replace it ASAP or you will find yourself stranded someplace, likely someplace nasty, in the near future.
DO NOT start a car that shows the tension assembly out of range! You will not be able to exchange the belt once you run it even a few turns. Running the belt WILL NOT make it fit. (You also want your hands and the pulleys clean as most stores won’t exchange a filthy item.)
As many of you may have noticed the serpent belt setup used in the 87-88 4 cylinder cars is not well covered in the Haynes or Chilton’s books. (At least not that I’ve ever found it.) The belt is easy to deal with as long as you keep a few things in mind.
The Fiero 4 cylinder Serpent belt requires no adjustment. Belt tension is controlled by a spring-loaded arm.
The one tool you should have is a “serpent belt wrench.” You can do without this tool but it usually means yanking the battery to get enough room to rotate a socket wrench. The belt wrench is made to fit into the confined space in Fiero and other such cramped cars. It’s worth the extra cash. ($15-30 US, shop around.) These are cheap enough that you can bend them for a custom fit to a given car, tho I think you will have to heat them to bend them.
To unload the belt tensioning arm put a 15mm wrench on the Idler Pulley bolt and rotate the wrench toward the battery. NEVER attempt to remove or rotate the bolt in the center of the spring arm!

Things to remember about serpent belts.
(Applies to all cars with serpents.)

• When properly tensioned Serpent sets will always out perform V-belts. This is why nearly all Serpent sets use a spring tensioning device. (See note at bottom.) It is critical the belt tensioning device work properly or belt life will be shortened tremendously. Because Serpent sets are carefully calibrated, life of PTO devices is also improved. The alternator, water pump, etc, are all protected from running with an over tightened or loose belt, which protects the bearings and sheaves from excess wear.
• These belts HATE oil grease and coolant. You’ll eat one up in short order if you get one contaminated and don’t clean it off. If for example you spill oil during an oil change and it gets on the belt or a pulley you must clean it up. To fully clean it up take off the belt and wash everything in citrus base cleaner or Simple Green. NEVER use parts washer or other solvent on the belt. (Brake Parts Cleaner will work well on the pulleys.) If you don’t get this mess cleaned up then the belt will glaze and start squealing. Once the belt squeals it must be replaced.
• Make sure the belt is running centered on the Idler pulley. In Fiero this is the smooth pulley that runs on the backside of the belt. If the belt is running off the edge of this pulley then the spring arm has likely gone bad and will have to be replaced. The spring arm cannot be serviced. (Only the bearing in the idler pulley can be replaced.)
• On some cars the Idler may be grooved and other pulleys may be smooth. All the pulleys must line up or you’ll eat belts. (The FWD applications of the 2.5 often have a smooth water pump pulley.) The belt must never be allowed to run off the edge of a pulley.
• Whenever the belt is off carefully check the bearings in the idler pulley, water pump, and alternator. (If present check the AC compressor.) If the bearings are sloppy, rumble, or feel “dry” as you turn the shaft then you have other problems besides the belt wearing.
• When installing the belt it helps to have someone under the car to hold it on the crankshaft and AC pulleys. These are hard to see and new belts tend to have a mind of their own about staying on them.
• On Fiero L4 and some others… Slip the belt over the smooth tension pulley last. Let the belt lay between the pulley and the wrench until it is around all the gooved pulleys.
• Keep an emergency belt and the wrench in the car at all times. For an emergency belt I recommend using the belt for cars without AC, even if the car really does have AC. This belt is easier for one person get on from the top with the least amount of mess. It will also give you backup if/when the AC compressor fails and cooks off the belt. (With the age of most AC compressors the chance of this is pretty high.) You can drive a car w/o AC but not a water pump or alternator. (It depends on the car. Fiero 4 cyl’s can be run with either the AC or non AC belt. Some cars can’t do that trick.)

Side note: Some cars use serpent belts in place of V belts, and also tension them the same way by adjusting either the Alternator or AC compressor. It is critical that these applications be correctly adjusted or the belts will not last.
Serpent belt material is much more picky about tension that V belts.

Belt Map

For those people that don’t have the belt map on the deck lid…

Why Does My Belt Keep Failing?

The first thing to check is pulley alignment and operation of the tensioning device. A critical factor here is that pulleys that are close together tollerate much less alignment error than pulleys far appart. An AC equiped Fiero will eat belts very fast if the crank, AC and Waterpump pulleys are just a little off. A non AC Fiero can take a more error as all the pulleys have longer belt runs.
Make sure every pulley is clean. Make sure nothing is packed into the grooves or built up on the peaks. Packed dirt will make problems.
Is oil or coolant getting on the belt? That will kill it fast.
How are you cleaning the car? Some cleaning and most wax products are bad for the belt. Fiero’s vent grates allow such products to easily find their way onto the belt. It wouldn’t be a bad idea to throw a cover over that side of the engine to prevent car wash products from getting on the belt. (Make sure the cover can’t contact hot exhaust parts! Remove the cover as soon as you are done washing!)
Check the AC compressor! If there is any missing or loose hardware, the compressor will move and alter the pulley alignment. Any alignment error will greatly shorten belt life but it is even worse with a high load item like the AC.
The belt’s life will be affected by the high heat in the engine bay. Depending on the setup of the vent grates, and a few other things, the belt may not last more than a year or two even if everything else is perfect. My experience, even with Fiero’s hot engine bay, is that the belts will last several years unless the pulleys have problems.

Checking Belt Tension

This works for most spring tensioners and will check your belt length as well without measuring anything.

• On the big round end of the arm where the pivot and spring are, there is a small arrow. It is hard to see and is often just a small triangle.
• On the arm mount, there is a gauge area. This often looks like V*******V or it may be a simple raised/indented bar on the metal. It can be hard to make out too.

Both marks are usually on the top part of the tensioner’s pivot area and shouldn’t be hard to find
once you clean the dirt off.
The image left shows the actual scale on an 87-88 Fiero L4 tensioner assembly. A new belt should have the pointer on/between the closer marks. (These marks will be slightly toward the front of the car on top of the tension assembly. The bolt hole you see is by the water pump.)
The pointer on the arm must be within the gauge area on the bracket. If the pointer is not in that area, the belt is not at the right tension and probably will not last long. Ideally the pointer should be in the middle of the gauge. If it is right at the low limit, the left end of the scale in the image, then it will probably move out of range as soon as the belt wears in some. Frankly If the belt is even close to the low limit, you want to replace it. Either it is very worn or significantly too long.

This belt doesn’t fit, the Catalog must be wrong…
If you can’t get the catalog belts on a car with a spring tension setup, you could have a few things besides a wrong belt. For the 87+ Fiery L4 here are some of the most common listings:

• Fiero 2.5L with AC: K060660 (Gates) 660K6 (Drive-Rite) 5060660 (Dayco) 4060660 (Goodyear)
• Fiero 2.5L no AC: K060615 (Gates) 610K6 (Drive-Rite) 5060610 (Dayco) 4060615 (Goodyear)

The Gates Goodyear and Dayco numbers are direct from their online catalogs.
Drive-Rite, a Dayco brand, is from PartsAmerica.com Oddly the Drive-Rite and Dayco cross references to Gates K060612, which is .29 inch shorter than K060615.
There is some tolerance in the system for variations in length. As long as the tensioner stays in the proper range, it doesn’t matter if one catalog says a hair longer/shorter than another. If you put a belt on that is at the bottom limit new, it could get out of spec once it runs in so make sure you check it after a few hours running.
Warning: The belt should easily slip onto the Idler Pulley on the Tension Assembly.
You should never have to fight a belt onto the idler. (Or whatever pulley goes last on other engines.) At the same time when you let off the idler, the idler should keep it tight. (Duh.) The range of acceptable belts is fairly small.
If the listed belts won’t fit, the first thing to check is the number printed on the belt. It’s not uncommon to have the belts get in the wrong package. The sleeve packing many companies use can fall off and sometimes the parts store or distributor puts the wrong belt back in the thing.
If you got the listed belt ok then you could have a bad belt tension device.
These often bind up with age and you may not be able to move them far enough to mount the belt. Don’t use a longer belt to get around this. The longer belt probably won’t be tight enough and could fail really fast. Go by the scale on the tension assembly! If the pointer is off scale the belt is too short regardless of catalog listing.
You could also have a replacement alternator or other device with the wrong size pulley. This is very common and why you need to check the pulleys on replacement parts. A small change in any one pulley can result in a belt change of an inch or more depending on the pulley size and how much belt wrap it has.
If a pulley has changed, it could cause you other problems. If the alternator is spinning too fast or slow there can be trouble. (Read Watt Story for more on that.)
There is some variation between how belts sit on the pulleys. This can be from one brand/type to another or even from one batch to another.
You may also suffer from “tolerance stacking.” In this case slight variations in mounting of the driven devices can require a slightly longer or shorter belt on the system. The alternator, AC compressor, waterpump and so on have some slop in their mounts. Over time and various parts replacements these parts may be in slightly different locations than original. These changes can add up in ways that make the belt path longer or shorter than the vehicle maker called for. The catalogs all list only what the vehicle maker said fits.

How serious is correct belt fit?

If you want to avoid this…

Make bloody sure that the tension assembly’s pointer is on the scale. Most if not all tension assemblies will not tolerate being pulled over range. If the pointer goes off scale low, the belt can go completely slack and be thrown from the engine.
To be more annoying… You won’t know until you try a given belt. There is enough variation that a 66 inch belt from one maker will sit a little differently and be ok while another doesn’t fit. Belt route will also be a factor. Bypassing the AC on the Fiero L4 can make it so all the 61 inch belts fit even when you have problems with some 66 inch belts.

How do I read a belt size?

The last or first three digits of the belt size tell you how long it is in inches and tenths. A 660K6 or x060660 (x varies by brand/type and isn’t very important.) is 66.0 inches long. The next two sizes larger are 665 and 670. 66.5 and 67.0 inches. (In my case the 670 belt has the pointer just a hair above the “middle” mark on the scale.)
An important note… The sizes that end in 5 are not always exactly .5 inch.
Dayco 5060665 is actually 66.6 inches according to Dayco. That means you need to check belt specifications.

Tension Assembly Replacement

Replacement assemblies should come with a gasket on the engine side. If the gasket is missing, you will have to make one. The gasket needs to be 3/32 inch thick. RTV Silicone WILL NOT work in this application!

1. Drain the cooling system. (The arm unit forms a cover on the front of the water jacket.)
2. Disconnect the battery and remove it.
3. Remove the top alternator bolt. (You may want to loosen the bottom one, the new tensioner may not line up exactly.)
4. Remove the Idler Pulley from the old and new tension assemblies.
5. Remove the old tension assembly and install the new one.
6. Replace the Idler Pulley on the new Tension Assembly.

If the new arm comes with a cork gasket then paint the gasket with Permatex High Tack, Permatex Super 300, or Balkamp Aviation sealer. This will fill any pours in the cork. A VERY THIN film of RTV Silicone will work if that is all you have handy. Make sure the whole area of the block covered by the arm base is clean before installing the new arm. If you pinch something between the arm and block you will likely damage the new arm or prevent it from sealing.
The new arm provided by Pontiac is built a little better than the original one.
You should only have to replace the part once in the life of the engine. (Keep in mind, because this arm is a cover on the water jacket it is exposed to full operational heat of the coolant. The old grease in the arm didn’t hold up well, and that results in pivot wear.)

Why Is There a Hole In My Block?

The large hole in the 4 cylinder that is covered by the serpent tensioning device is the opening for the water pump when this block is used in other vehicles. In most FWD versions, the hole has a steel cover bolted over it. The only variation I’ve seen use the hole is the S-10 truck. (I’m not sure if S-10 is exactly the same block or not.)

The TBI used for 87-88 Fiero 4 cylinder motors is the 700 series unit presently manufactured by Delphi Automotive for GM.
You can find Delphi’s public relations info for the 700 TBI here. The information includes images and general specification data. The articles that we’re interested in at the moment are “Throttle Bodies – Single Point” and “Throttle Bodies – Multec Bottom Feed.” The first is the TBI unit and the second is the injector in more detail. Fiero uses the low-pressure version. (Note: Delphi changes things fairly regularly. If they still exist, these documents may be hard to find. I can’t post them due to copyright.)
Below you can see how the TBI is setup and where some of it’s components are.
I also noted the MAT sensor for you. (MAT is also covered in the DIS article.)

• FPR, Fuel Pressure Regulator
• TPS, Throttle Position Sensor
• IAC, Idle Air Control motor
• F In/Out, Fuel Lines
• MAT, Manifold Air Temperature

The design of this TBI is really something. It can tolerate amazing amounts of crap in the fuel system without plugging the injector. There are screens right on the injector. You’d have to cover them nearly completely to block off injector flow. To get that much trash to the TBI, both the main filter and the pickup sock in the tank would have to fail or you’d have to have major corrosion damage to the inside of the fuel lines.
The 700 TBI is comprised of two modules. The upper section handles all the fuel metering and is the same regardless of what lower section is used. The lower section handles all the air metering and contains the throttle plate and IAC. There is no fuel flow between the modules except what flows from the injector tip. 700 TBI bore diameter is determined entirely in the lower section.
(If you were punching out a 700, you would only machine the lower half. The lower section, assuming there is enough metal, can be punched to the maximum diameter of the upper half.)
BTW, the TBI used for 87 and 88 Fiero L4 has a 45mm diameter main bore. The largest Delphi makes is 48mm. You could install a 48mm one but you’ll need to ream the manifold and you probably won’t gain much power.

Do I need to use injector cleaner in my gas?

Probably not. The cleaners already present in most pump gas should be more than enough. Keep in mind that this injector is not being heat soaked like port injectors are after engine shutdown. It’s far from the intake valves and upstream of the throttle as well. That prevents fuel residue from cooking onto the injector.
The only time I can think of where cleaner might help is if the car sat parked for a long time. That should help wash away anything caused by stale fuel.
With this system, if you are finding allot of carbon in the TBI and intake then you have problems developing that need more than some cleaner. (You will likely also need to check/replace the MAT sensor.)

Throttle Position Sensor

The TPS is not adjustable. The ECM is programmed to accept any slight variation in the home position of the sensor and recalibrates the home position each time the engine is started.
The TPS does wear over time, but it should last many years under most conditions.
Do not attempt to clean the sensor and never spray it with solvents or pressure washers.
The easiest way to test the TPS is to use a sewing needle to probe the terminals. It’s long and very thin so you are less likely to cause a short if you slip. Simply slip the needle between the wire and the seal. If you short the terminals to anything you could fry the ECM!
One terminal will show 5V. Another terminal is ground. The last is the output.
The TPS output should show less than 1.25 volt when the TBI is at idle. Output voltage should increase smoothly between idle and WOT. (Note: It is usually easier to test the sensor with an analog meter. Digital displays are often too
jittery.)

The Injector

Note: Don’t rely on the visual appearance of the injector output. In most cases you won’t be able to tell a good spray amount/pattern by eye. These systems nearly always look like shower heads when running. Keep in mind that unlike port fuel injection, fuel from the TBI has plenty of time to mix on the way to the cylinders. The TBI is also on a heated manifold just like a carburetor uses.
If the injector is leaking it will tend to do that as soon as the system pressurizes. The most common leak is O-ring failure but it is possible for the injector to leak internally.
The injector used in these is built like a tank. I don’t think I’ve heard of more than one or two that was actually bad. I’d say 99% of the time if the injector weren’t firing that you need to check the fuel pressure and the signal from the ECM.
If the injector is leaking, make sure it’s not one of the two O rings. The O rings are more likely to fail than the injector. If the O rings are bad, then I’d rebuild the TBI and replace all the other stuff as well.
There are test (“noid”) lights for the injector used in the 700. Use them! A single noid light costs around $6 while the injector costs $75 to $100 or more.
You can get noid lights at many parts stores. You can get whole sets of them online from various sources.

Idle Air Control motor

Contrary to popular belief the IAC is very well designed and will last nearly
forever under most conditions. If you think there is an IAC problem your first project should be checking for vacuum leaks and EGR problems.
DO NOT spray the IAC with “carb” cleaner. If you must try to clean it, use electronics parts cleaner. Strong solvents can eat the insulation off the coils.
You can now get test (“noid”) lights for IAC as well as the injector. I’ve seen these for about $10 at Pep Boys.
Ideally, you’ll use an IAC noid with an ECM scanner. The lights on the noid should match whatever the scanner says the ECM is doing. The quickest test is to plug in the noid light and create a small vacuum leak or turn on the AC. (If the AC works…) Either one should cause the ECM to try to adjust the IAC. Even simply moving the throttle some should create an IAC change.

When does the IAC reset?

Per GM service documents:

The IAC valve will be reset by the computer when the vehicle speed exceeds 43 MPH while the engine speed is above 2000 RPM.

Or

When the diagnostic test connector is grounded when the engine RPM is above 2000 RPM.

Fuel Pressure Regulator

The fuel pressure regulator is very unlikely to fail. If/when it does, it usually leaks externally. It could be possible for something to get trapped in the regulator and hold it open. Corrosion of the regulator valve and seat are unlikely. They appear to be Stainless Steel. Keep in mind that if you remove the regulator that it may not seal reliably when you put it back on. Do NOT use gasket sealer on it! If it leaks then it needs to be replaced.
The fuel pump on the other hand is a common failure item, especially if you’ve run the tank dry. The fuel flow cools the pump and it won’t take long to cook when running dry. (This is true of the many kinds of pumps, not just fuel pumps.)
The quick test for no or low pressure is to pinch the fuel return line and see if you get pressure. This may help if the regulator is blocked open but probably won’t do a thing if the pump is batty.
There is a fuel pressure gauge set available for TBI and other low-pressure systems that don’t have Schrader valves. The set includes and adapter that save you from cutting the line to install a T. These sets are expensive, typically over $50. You may be able to borrow one from some parts stores. (The expensive part is the adaptor that installs between the fuel line and the TBI body so you can connect the gauge.)

Fuel Filter

It’s under the car and can be a real pain to change.
You want to change this every so often, like once a year or so. These filters are built like a small oil filter internally and hold a tremendous amount of garbage.
The only way I can think of that you could plug the thing are if the fuel line is going bad or if the pickup sock in the tank fails. If you seem to loose fuel pressure after the car runs for a while, the filter could be the problem.
If you are going to remove the filter for any reason then just replace it. They don’t cost very much and you can usually get them even cheaper at places like Wal-Mart.

Repair & Rebuilding

When installing the IAC motor, make sure the pintle is retracted. DO NOT force the IAC motor into the throttle body! If the IAC motor will not easily seat fully in the body then the pintle is too far out. You should be able to seat the motor fully into the throttle body with little effort.
Carefully check the TBI mounting holes in the manifold. These holes can be damaged if the air cleaner has impacted the trunk wall. (Read the torque strut article.) If the holes are stripped you’ll have to use Helicoils on them.
If the throttle shaft is badly worn, find another TBI unit. You should be able to find these fairly easily at any salvage yard. Otherwise the 700 unit is very easy to rebuild.
Don’t mess with the idle stop during rebuild! There’s no reason to fool with it.
The rebuild kits include the fuel pressure regulator diaphragm. If the FPR diaphragm is bad then just buy the rebuild kit and be done with it. The kit isn’t that much more than buying the diaphragm and you get all the gaskets, O rings, and screens. You essentially end up with a new TBI unit.
The rebuild kit usually comes with more gaskets than you will use. The last one I bought came with three mounting gaskets and two body gaskets. You should use the replacement gasket that matches the original.

Assembling and Mounting the TBI

When you put the two halves of the body together torque the screws to specification.
After you torque the mounting bolts, check the body screws again and torque as needed to reach specification. The mounting bolts often cause the body bolts to loosen. If you don’t check them the upper body could warp and cause an air leak.

(Source: ALLdata)
In case you don’t have a VECI label on the deck lid… Here’s how the vacuum lines connect to the 700. (It’s a photo of my VECI label that I was farting around with.)

Documentation

The 700 TBI is not covered in the Haynes Fiero book. Haynes does cover the 700 in their 86-96 Fuel Injection book. (Haynes # 10220) This book covers both versions of TBI used in Fiero. Amazon lists the book as out of print but it can still be found in many part store inventories.
The only other book I know of that documents this unit is the Helm shop book.
While expensive, these books cover all the year specific items left out of Haynes and Chilton. They also carry replacement Owners Manuals and other info.
ALLDATA DIY is a good source. This is the online version of the CD/DVD product they are well known for. While you can work directly from their data, I usually consider them a supplement to other sources, including the Helm book.
ALLDATA has all the TSB and Shop Manual updates you just can’t get anywhere else. If the online version allows printing, I’d say join them for a year and print everything you can get your hands on. (I strongly recommend a laser printer over an ink jet. Most ink jets are likely to eat multiple cartridges doing this.)

Adjustment Procedures

The only adjustment possible on the 700 is to the idle stop screw. With the possible exception of new replacement units, there is no reason I can think of that you should ever adjust the idle stop. All the ones used on 2.5 liter motors should transplant without changing the idle stop.
The only reason I’m covering the idle stop adjustment is because every so often you run into a motor where some hack has screwed it up. You’ll know if that’s happened because the Idle Stop seal will have been removed.

Idle Stop

You’ll need an ECM scanner to verify the IAC position.

1. Jumper ALDL terminals A & B.
2. Turn on key and wait 30-60 seconds. This will close IAC pintle.
3. Unplug IAC while key is still on.
4. Turn key off and remove the ALDL jumper.
5. Start car and set idle stop screw.

The Haynes EFI book says set the idle according to the VECI label, but of course the VECI label doesn’t say anything. Near as I can tell… If you set the Idle Stop for about 800-850 RPM then the IAC should be able to do its job properly.
Once you are done, shut off the car, plug the IAC in, and clear any errors that may have been set in the ECM.

Performance

This section is mainly a bunch of pondering. I’m still looking into most of it. I thought I’d put in what I had in case it’s useful to someone who wants a bit more power from the DIS motor. (It could also be useful to someone replacing a fried DIS motor…)
As I mentioned above, the Fiero TBI has the 45mm main bore. You might be able to find a 48mm unit to install. How much power you’d gain from that I couldn’t say but it’s something to keep in the back of you head if you are building up a DIS motor. It may be possible to bore out a TBI unit but I wouldn’t hold me breath on it. It’s not something you can do without a good machine shop.
If you do go looking for a 48mm unit, check the intake manifolds and head of later model DIS L4 as well. This could save modification of the stock manifold and may give you larger intake runners etc.
The reason I say this is that GM specified the 91 Olds Cutlass Calais (VIN U?)
Iron Duke at 112HP. I’ve seen that motor once and only externally. It looked identical to the 1988 engine. (Balancer motor.) They had to ring out the extra from someplace.
In reality, you’d be better off seeing if the 1991 engine would work in Fiero and then building that up if needed. That gives you an engine 5-6 years newer as a base. I couldn’t see why it would not but I haven’t been able to really dig into one yet. You should be able to get one for about $200-300 from a local salvage yard. (I believe 1991 was the last year for this engine.)
If you do that, make sure you also get its ECM! The PROM chip has information in it that may be needed. I’m pretty sure the thing still uses the same ECM as Fiero. Assuming the ECMs are the same, the VSS flag in the PROM isn’t. You’ll have to trick the ECM or burn a new PROM with the correct VSS flag. (You could just use the Fiero PROM but you’d loose updated code in the 91 PROM. The original Fiero PROMS have a few minor issues…)

Fuel Pressure

According to what I’m told, you can make the fuel pressure regulator adjustable. If you try this, do it to a spare regulator cover. It involves cleaning out the sealer/solder over the regulator screw. You may also need a longer screw and a jam nut to prevent the pressure from changing due to vibration.
(Someone in the forum did this once. I forget who…)
To tune it, you’ll need a fuel pressure gauge and a chassis dyno or a Gtech unit
You really don’t want to do this by feel alone.
The idea is to start from OE pressure and tweak the thing up a little bit at a time until performance peaks. (It’s a bit more involved than I’m covering here.)
Keep in mind that if you restrict fuel flow too much you could burn out the fuel pump!

4 Cylinder Timing Gears

NOTICE! This is an unfinished document. It is a collection of all the stuff I’ve come up with tested or not… USE IT AT YOUR OWN RISK!

Anywho…

Cam jobs suck under the best of conditions. The majority of FWD and Fiero cams are never fun to work on. Here’s a collection of stuff I’ve gathered up that should help.
One item that surprised me… GM actually built the 87+ 4 cylinders with a simple steel crank pulley. As cheap as GM is, that one was still surprising.
Harmonic balancers are usually considered a critical part of the crank set. The good news is they did revise the parts list and you can get a real harmonic balancer for them.
I’m working on methods for changing the cam pulley using common tools. I’ve included that material here even though it’s only in the development phase. I figure there’s enough there that more advanced people can use or adapt it as needed. I’m sure there is some kink in it that still needs a good beating.

UPDATE

Back On Holiday has posted a large number of pictures he shot while doing his timing set.

• Here’s the original Forum Thread. This thread has grown to 2MB plus in size and may be difficult for some readers to download. (IE Users, Right Click stubborn images and then click Show Picture.)
• I’ve created a compact version of the thread here. This version is less than 800KB.
  • The images are smaller and I adjusted brightness and contrast to expose more detail.

I’ve also consolidated the GM parts listed here and in the forum. You can get them at GM Parts Direct. (This table doesn’t include Vin U parts.)

Source: GM Parts Direct. Prices as posted 12-Mar-02.
I recommend a new thrust plate anytime the gears are replaced. A crappy thrust plate isn’t going to help your new gears any. For less than $6 it’s cheap insurance.
It appears that the newer thrust plates have added holes to help with oil distribution in the hub area. I don’t know if the hole in the oil gallery plug is still needed with the new thrust plate. I tend to lean toward adding the hole because it should also get more oil to the gear teeth. I don’t think the revised thrust plate would help that.

Revised Parts

Quite some time ago, GM changed the timing gear numbers from individual parts to mated sets. If your 22P book or other old list shows them as separate parts, those numbers are invalid. Always replace the timing gears as a set no matter where you get them! The crank gear may look ok but even subtle wear can cause a problem with a new cam gear.
GM revised the crank pulley on later model 2.5l. The original is simply a steel pulley with no harmonic balancer function. In Fiero this applies to the 87-88 4cyl. I’ve also included the U VIN version of the 4 cyl for those that may have acquired one thru an engine swap. [My notes in square brackets]

“It is also recommended that a crankshaft torsional damper [AKA Harmonic Balancer] be installed along with the [timing] gear set. The damper reduces critical crankshaft vibrations thereby decreasing [gear set] wear. When the new damper is installed, the old crankshaft pulley may be discarded. If the engine already has a damper, it should be reinstalled.”

Source: GM TSB 90-6-21, Dated 02/90, Servicing Camshaft/Crankshaft Gears (Install Torsional Damper)
I’ve given both the GM timing set number and the damper number. I don’t know what the damper costs from the dealer. I have found it in inventory for the 87+R motors, so it’s still out there. I’ve also listed 3 third party replacements at the end of this page.
Harmonic Balancers are just plain good for the motor. They reduce timing gear and crank bearing wear and may give slight improvements to fuel economy and HP. Installing the new balancer is strongly recommended.

Fiber (Phenolic) vs. Metal Cam Gear There is a ton of debate over replacing the Phenolic cam gear with a solid metal one. While many people say a solid metal gear is better, I have my doubts.

Here are a few things to think about…

Various types of composite gears have been used in timing sets since at least the mid 60’s that I’ve seen. They may go back further than that. My 1968 289 Ford motor had a nylon tooth driven gear in it’s chain set. There’s allot of well-established technology behind using these gears in the Fiero motors.
The original Phenolic cam gear is lasting well over 100,000 miles and a dozen or more years in most cases. The odds are good the next one will outlast the rest of the engine and for many people, the rest of the car.
If you think 100,000 miles is too short a service life, consider that most timing belts in other motors have to be replaced at 40,000-mile intervals. Such belts are often as difficult or worse to replace than the “Iron Duke” timing set.
If/when the timing set fails in this motor; there is no significant damage to the engine. This is much different from many other motors where timing set failure can literally destroy the engine. Such “Interference Engines” are known for snapping valves and driving them thru the head block or pistons.
Phenolic gears have inherently smoother teeth than metal gears and generally stay that way over their life. This is another factor that allows tighter tooth clearance than metal on metal. Remember, gear teeth are by nature also bearing surfaces. The smoother they are, the less friction they develop.
Metal gears are prone to galling if tolerances become excessively tight or they aren’t getting plenty of oil. This can result in sloppy timing or even gear failure.
Part of your decision should probably include which engine setup is in the car.
Flat tappets will put more loads on the cam than Roller lifters will and that might shorten the life of the Phenolic gear.
The distributor will also increase cam gear load. Even in the distributor motors the Phenolic gear has been lasting 100,000 miles or more. In most cases, by the time the motor wears out a second gear it’s going to need a full rebuild.
Some people have indicated metal may be more noisy. If the gears are well made this should not be much of an issue. This is a helical cut gear. Such gears have more than one tooth in contact at any given time. This makes the transition from tooth to tooth much smoother than with straight cut gears.

What kills the gears?

Obviously simple wear is a big factor. The lack of a harmonic balancer on some versions of L4 could also be an issue.
As originally installed the gears apparently don’t get a large amount of oil. GM recommends a change to improve gear oiling. I strongly recommend that change be done. As I understand this, the only oil the gears get normally is whatever runs from the cam and crank bearings. The change punches a small hole in an oil gallery plug to get more oil to the gears.
Frequency of oil changes and choice of oil are also likely factors in this. If the gears are running a little dry to start with then crappy oil won’t help any.
Running heavier oil than specified could also be a problem. Heavier oil could increase oil pump load on the cam and reduce oil to the cam and gears at the same time.
When the cam gear fails other items to watch out for are the oil pump and, in the older motors, the distributor. Make sure you check both items when changing the gears. If either or both are binding then you could be overloading the cam gears. Installation of metal gears may only hide such a problem until the offending part(s) fail completely.
The endplay on the gears is also important. Too much and the cam could wander in the bore. Too little could make the cam bind. This item is very important to watch when changing gears.

Do I need to remove the oil pan?

NOTE: To clarify, Yes, I think you should probably drop the pan. Besides cleaning it out, you can check for pump problems before they kill the new gears, or worse. Interestingly, the GM gear change TSB doesn’t require this.
It’s a good idea but I don’t think most people do it. Also depends some on just how much was chewed from the gear.
Since the engine quits as soon as the cam gear does, allot of the waste is probably sitting right below the gear. Once the cam and crank gears are off you can probably get most of it out that way.
The big pieces of phenolic tend to sink to the bottom of the pan and sit there but if you think you’ve got allot of small particles you may want to do the pan.
At the very least, I’d change the oil after you fix the gears. You could use some kerosene to wash stuff into the sump that you can’t get out by the crank.
Changing the oil should remove anything that floats.
I also recommend a magnetic oil plug to help grab any metal from the drill and tap operations that may escape the rag. (I always run a magnetic plug.
Whatever it catches is that much less that passes thru the oil pump.)

Do I need to remove anything else?

Disconnect the battery cable(s), and if needed the dog bone. You don’t want to risk tugging the battery if you drop the motor any. The dog bone has to be loose to drop the cradle or remove the motor mount.
You may want to take out the strut and hub assembly to gain workroom. As long as you don’t separate the hub from the strut you should not need an alignment much if at all when you are finished.
You’ll probably want the mud skirt removed.
You can gain a couple inches by removing the motor mount. Just make sure you don’t rest the motor on the crank pulley. This may give you enough room for that you don’t need to drop the cradle.
To remove the motor mount, I reach in from the wheel well to get the top nuts. You can get one nut with a socket wrench but the other doesn’t have room. I use a 15mm flare fitting or box end wrench on that one. These are locknuts so they are going to be tight all the way off and back on.
You can gain more room by dropping the back of the cradle a little.

Remove and Install

Whenever the timing set is replaced, replace the crank seal while the timing cover is off. If the sealing area of the existing pulley or balancer is scored,
replace it or install a repair sleeve. (Clean all parts with alcohol or brake parts cleaner before installing the repair sleeve.)
Always replace the crank seal when installing a new damper!

Modified GM in car method

Please Note: This procedure should be considered “under development.”
Until I can obtain a test cam and gear, or (GAG!) my gear fails, I can’t test this. So while it should work, and it is based on a GM TSB, I just don’t have all the facts.
Based on a method originally published in GM TSB 88-6-62 dated 6/88, this version has been modified to allow common tools. (The original GM TSB is available by subscribing to ALLdataDIY.)

The logic behind this

GM’s method uses two 1/4″-28 bolts threaded into the metal hub very close to the cam and the PFKB method farther down appears to thread the access holes in the cam gear. I don’t see why a standard puller, used in close to or even partly biting the hub should be any problem. (The big holes allow access to the thrust plate that keeps the cam in place)
The Lisle steering wheel puller may even allow you to use GM’s recommended pulling bolt size and locations. You’ll probably need washers for the bolt heads.
GM has you start the holes with a small bit, enlarge them to the tap bit, and tap to 1/4″-28 with a blind tap. I forget how deep the holes are supposed to be.
They don’t go all the way thru.
The most important item is making sure GM guidelines are followed for the cam hole. If the hole is too deep you could weaken the cam. Too shallow and you may not have enough bite to press on the new gear.

Things you need

This procedure requires a high-quality steering wheel puller such as Lisle’s #45000. Cheap pullers may be destroyed in this application. You may be able to use a small harmonic balancer puller. (Lisle’s puller lists for $16.95. How much cheaper can you get and still have a good tool?) Don’t forget to oil the puller’s drive bolt before you start! (This version assumes you will use the Lisle 45000 puller. If you use a different puller you may need a different drill and tap to match your draw bolts.)

The Lisle 45000 puller contains the following parts:
45020 Puller Screw
45050 Screw Pad
45090 Puller Frame
(2) Washers
(2) 45200 3/8″ – 16 Bolt
(2) 45210 5/16″ – 18 Bolt
(2) 45220 5/16″ – 24 Bolt
If you can’t find Lisle tools at your local parts stores, try Sears. My area Sears had a bunch of Lisle stuff in stock when I was there last. (Don’t go by Lisle’s dealer list. Allot of parts stores buy from jobbers and often aren’t listed by Lisle.)

You’ll also need:

A 3/8″-16 “Bottoming”, AKA “Blind,” tap and it’s matching drill bit. Good taps nearly always have the required drill size engraved on them. (Unlike a regular tap, a bottoming/blind tap will cut threads all the way to the bottom of a hole that is closed or doesn’t have enough clearance behind it.)
A smaller bit, like 1/8 inch, used to drill starter holes may also be helpful.
Some 3/8″­16 threaded rod and a matching nut. (A bolt with long enough threaded length and matching nut will also work.) Consider a Grade 8 hardened rod/bolt for this. (Class 10.9 if your using Metric stuff.)
A 1mm (.040 inch) drill bit.
A dial gauge with suitable mount.

The process

NOTE: The hole in the cam MUST NOT exceed 1/2 inch deep! That holes dimensions are very important and were determined by GM to leave the cam strong enough to accept the new gear and not break later. Use depth stops or at least tape on the drill bits to prevent going too deep. The hole in the cam may be easier if you first drill a smaller pilot hole.
Drill and tap all three holes before removing the cam gear. This will help keep trash away from the cam bearings. Be careful drilling thru the gear. Slide some sheet metal behind the gear to protect anything you may hit with the drill.
Rotate the gear so you aren’t drilling over the cam thrust plate!
Take your time tapping the holes. It may be easier to use a standard tap to start the hole and follow it with the blind tap to finish. A regular tap definitely won’t give enough thread in the cam hole.

Stuff rags into the oil pan to collect
waste from drilling and tapping. (A single large rag is best.)
Use the scribe lines to drill and tap two holes in the cam gear. Get them in close to the gear’s hub. The phenolic is strong but you want as much grip as possible for the draw bolts. (Make sure you don’t get so close the drill or tap will hit the cam!) This may be easier if you drill pilot holes first with a small bit. If you hit the metal hub, that’s ok. It’ll just give more strength to pull against.
Drill and tap a hole in the center of the cam.

Install the puller. Cover the hole in the cam to protect the threads! (If you can’t use the screw pad that comes with the puller then use washers or coins.)
Slowly pull off the gear.

While the gear is off…

(This is from the same TSB with the gear replacement instructions.)
GM recommends that a 1mm (.040 inch) hole be drilled in an oil gallery plug to
improve gear oiling. I DO NOT know exactly where this gallery plug is! The hole can be smaller but must not be bigger than specified! (Later versions of L4 may already have this hole.)

Install the new gear

Use some large washers with the threaded rod and nut to press on the new gear AFTER installing the crank gear. Oil the threads before you press the gear.
Make sure the timing marks are lined up!
Set up the dial gauge so it touches the end of the cam. Per the GM TSB, the cam should have .0015 to .0050 (inch) of end play with the gear installed.
Make sure all the rags are removed from the oil pan and install the timing cover, balancer, etc.

PFKB Method

PFKB has a tool set you can purchase for replacing the cam gears. This is another variation on the GM method. I don’t know anything more about their kit than what is on their web site.

Yet another Method

This one is just a theory. As long as you’re very careful there’s no reason it can’t be done like this. There are loads of variations possible here. This is the one idea I was playing with recently.
It should also be possible to “crack” the cam hub for removal. This could give you a way out if no pullers are available. Someone mentioned grinding in a forum thread… I would not do that. Grinding or power saws would likely throw stuff everywhere.
To install the new gear you will still need the hole in the cam, etc. (As described above.)
To do this use a fine drill bit to drill a series of holes in the hub. Drill the holes so they are about 1/8 to 3/16 inch from each other. Exact distance will vary some depending on which bits you choose to use. (Fine bits are easier to control.)

WARNING! Make sure you do not drill over/into the thrust plate! Use a depth stop to make sure the drill can’t hit any thing behind the gear. Use a piece of sheet metal to shield the area behind the gear. Adjust the stop as needed to prevent drill contact with the cam, bearing or block! You’ve got to be very careful drilling the holes near the cam!

It seams like allot of holes at first but you save a bunch by making use of the access holes cast into the cam. (The holes let you get at the thrust plate bolts during cam removal.) The gear itself is fairly soft so drilling those holes should go pretty fast.
Drill the first hole close to the cam and the rest straight out from it. The holes don’t have to be perfectly straight. Make sure you don’t hit the cam with the drill. (You may need 2 rows of holes like this.) Once the little holes are done, use a larger bit to connect as many of the small holes as possible.

The fiber is actually covering part of the metal core. You’ll need to make the line of holes reach at least to one of the access holes molded in the gear. You may have to go all the way to one side of the gear.
Once you’ve made a line of holes and enlarged then as indicated, use sheet metal screws/bolts to spread the crack. Work from the outside of the gear toward the core. (You want pointed screws not tapping or drill tip screws.)

In car cam removal

By dropping the rear of the cradle, it is possible to remove the cam without pulling the motor. A number of people have done the gear change that way.
There are several accounts of this in the forums. Be extremely careful that you don’t damage a cam bearing when extracting or inserting the cam.
In car cam removal is pretty tricky. I’d strongly recommend you try one of the other methods. Disturbing a used cam can have unpredictable results on high mileage motors. Make sure all lifters and pushrods are returned to their original locations. Put nylon wire ties on the pushrods before you remove them so you know which end goes up later. Buy or make a tray to keep everything in order.
You may need to remove the alternator and/or intake manifold to get enough room to work on the lifters. The rest of the procedure is essentially the same as published in Haynes etc.
There is an advantage to cam removal… It allows full inspection of the cam and lifters. This would be more important to flat tappet setups than rollers. It’s not at all uncommon for flat tappets to wear cam lobes completely flat.

Other Info

Third party damper sources for 87+ VIN R, replaces 10101369.

Even though Damper Dudes is new, they also rebuild them so they want the old ones. That could be a problem since many people only have a steel pulley, not a damper. Parts America does provide a picture so you can see what the new damper looks like.
Autozone only sells new dampers. I’d recommend new because you also know the pulley is fresh. A worn pulley won’t help belt life… Serpents can be a big enough pain without adding an iffy pulley.

Repairs many common Fiero wiper problems. Erratic or non existent delay action, phantom wipes, 3 wipes per wash cycle irregularities.

Phantom wipes are caused by wear in the switch assembly in the steering column. If the wear is too great this kit may not stop all the phantom wipes. The only cure will be to replace the wiper switch which not an easy job. Considering the cost and effort required to replace the wiper switch in the column it is best to first replace the capacitors on the delay board to see if that eliminates the phantom wipe problem. In most cases it will certainly eliminate a large percentage of the phantom wipes.

There are generally only 2 delay wiper boards used on the 1985-1988 Pontiac Fiero. Board number: 22048550 and board number: 22062692/22062693. If you have a delay wiper board that is not one of these listed it may not have the required parts included. Please email me for more info if you find a board with a different number other than the two listed above. This kit contains enough parts to rebuild one or the other. Some parts will not be used. Includes a length of .032″ 60/40 solder which is preferred for circuit board repairs. A pencil soldering iron is required. A soldering gun is too hot and large for this type of soldering.

There are two major problems that affect tthe Fiero wiper / washer systems. One is the dried-up capacitors on the pulse board and your rebuild kit deals with that very effectively.

The cure for these bad wiper switches is to replace them with the wiper switch for ‘87 or ‘88 Fiero’s. That switch is mechanically and electrically compatible – it’s a drop-in replacement. They’re also less expensive than the early version switch (go figure). This will solve the problem and prevent it from returning. This is the switch this is in the steering column under the steering wheel, not the cruise/turn signal stalk.

You can remove the appropriate terminals from the warning chime connector to selectively eliminate whatever circuit you don’t want. looking at the flat side of the black connector

——
8765
4321
——

1. Pink with black stripe -ign. input
2. Yellow-seat beltlight in dash
3. Black-main ground
4. Black-seat belt warning chime
5. Tan with white stripe-park-brake chime
6. Light green-key in ign.chime
7. Range 2 wires-power input
8. Gray-lights are on warning chime

Okay, once you get the “blue bingy thingy” working… You can take the cover off, and bridge the resistors (brown cylindrical things with colored stripes) with different value resistors, and make the “bings” into “bongs”. You can also speed up and slow down the “bing” (or “bong”) rate. You can make your car sound like Big Ben. (Well, not really, but sorta.)
(It’s a “geek” thing. Sorry.)

by Ray Paulk

The gas gauge on a Fiero seems to be a PITA (Pain in the Butt) for all of us. I ran out of gas 5 times before I broke down and decided to fix it. It didn’t take too much investigation to figure out that the problem is with the sending unit which is part of the fuel pump assembly inside the tank. Having dropped Fiero gas tanks before I was none to anxious to jump into this job. But when my fuel pump failed and I was forced to drop the tank, I figured that I might as well fix the sending unit too.

The fuel gauge sending unit for the fuel gauge is a simple potentiometer which varies its resistance with the level of the fuel in the tank. It’s supposed to read 0 ohms when Empty and 90 ohms when Full. The problem is that this “pot” never seems to get down to 0 ohms and always goes much higher than 90 ohms. Of the fuel gauge sending units that I’ve have removed, they usually read about 15 to 20 ohms with the float all the way down (Empty) and about 120 ohms with the float at the top. This means you’ll run for quite a while with the gauge reading Full and run out of gas when the gauge reads 1/8 to 1/4 tank. Sound familiar?

A potentiometer is a variable resistor. Its comprised of a resistance coil and a “center-tap” or “wiper” which slides along the coil. The resistance is measured between the center tap or wiper and one end of the coil. As the wiper moves along the coil, the resistance between the wiper and the end of the coil changes. Right at the end, under ideal conditions, it reads zero.

The potentiometer of the fuel gauge sending unit is made from components. The resistance coil is literally a 1/16″ fiber board about 1/2″ wide with a resistance wire wrapped around it. The “wiper” of the pot is tied to the tank float. As the fuel level rises and falls, the wiper moves along the edge of the coil and varies the resistance between the wiper and the top end of the coil. (The float goes down and the wiper goes up.) There are fine tune adjustment screws which actually tilt the coil board in and out to change the contact point of the wiper but its not enough to really fix it.

The problem is that the wiper never gets down to the bottom coils of the resistor to read zero. The fix is to “short” the bottom coils to meet the point where the wiper contacts at its bottom most position. Here’s what to do:

Remove the sending unit from the tank. (Not a really fun job but necessary.) The wiper mechanism and resistor board should be fairly obvious they are probably under an aluminum cover which is easily removed with bend tabs. Note the screws with the springs on them at the top and bottom of the board. These are the adjustment screws. Note that the last coil of wire falls under the spring on the screw. This is the contact point.

Although you can bend things to try to make it work, this might damage parts and is often ineffective. You may break something. Another “not recommended” technique is to remove some coils at the bottom. Here too you can get in trouble by breaking the wire or loosening the coils. Also, to get to zero ohms, the wiper would have to slide to the last coil and perhaps off the coils all together. Not a real good solution.

The better way is to first set the adjustment screws to a neutral position 1/2 way through their adjustment. Now mark the lowest point the wiper goes on the coil (mark with something like a “Sharpie” pen.)

On the side of the board, you will have to clean the surface of the coils because you are going to make a solder bridge from the last coil to the coil where the wiper last contacted. I either use a wire wheel in my Dremel tool or a fiberglass burnishing brush which I got at Radio Shack (Cat. No. 64-1986). When you have the varnish removed from the coils and they are clean, coat them with solder flux (plumbers paste) even if you use resin core solder. This wire does not like solder. I even use Muriatic acid to help clean the wire. Then solder all the last coils together. Note, this is electronics work, not work for solder guns or torches. If you don’t have a “pencil” type, electronics duty soldering iron, you may be better off going to an electronics store or TV repair place to have this done.

Now remount the coil board. Naturally clean the springs and screws for better contact. (0 ohms is tough to get … when you want it). Attach ohmmeter to the gauge out put terminals (they should be pink and black, at least in the wiring harness. If not, they should be obvious if you’ve gone this far.) Hold the float as low as it can go and run the upper adjustment (empty position) screw in and out to see what the lowest ohm reading you can get it. On mine I got 1.9 ohms. I turned the adjustment screw in on my units until I got a consistent low reading of 1.9 ohms. I then backed it out ’til the ohms started to climb. You want to set this adjustment right at this break point.
Now do the same with the lower screw ’til you get 90 ohms with the float all the way up. When you get this “Full” output set, go back and recheck the Empty set point. You’ll probably have to do this a few times as one setting affects the other. Remember that the bottom must be set right at the break point mentioned earlier. When you get both ends set, your sending unit is calibrated.

Now you can pop the cover back on the resistor coil, drop the sending unit/fuel pump back into the tank and “throw the tank back up in place. (Ya, I wish it were that easy. I always tend to cut the heck out of my hands when I do this. It’s trying to get all those damn tubes and hoses back on that’s a killer.)

If you did the job right, your gauge will be correct. If you still have problems, you can check the gauge with a 90-ohm resistor and a solid wire. Remembering that the pink and black wires are the sending unit wires, you can put a 90-ohm resistor in place of the sending unit. The gauge should read Full. Then put a solid jumper in and the gauge should read Empty. If it doesn’t, your gauge is messed up. But a bad gauge is seldom the problem.