4.3L S10 to Fiero Engine Swap

4.3L S10 to Fiero Engine Swap

Old Engine Removal

Sorry, I didn’t have my digital camera when I started actually tearing into the car. But never fear, I still have some pics to share of the end result.

The car was backed into the garage to start teardown. Mind you, this is an un-heated garage and I am starting the swap in mid-December in Wisconsin. Do I get a point for that? Anyways, teardown pretty much followed the Chilton manual I have…pretty much. This is how I did it, some steps may vary on your particular car and patience level.

1. Remove deck lid & side covers – makes for much easier access when changing plugs, too…

2. Remove Battery and disconnect ground straps.

3. Soak cradle bolts with PB Blaster.

4. Drain coolant into suitable drain pan. Keep away from animals.

5. Remove air cleaner.

6. Disconnect throttle cables. My cable was shot and being a bi$%h so I just cut it.

7. Remove heater hose at intake.

8. Disconnect vacuum hoses.

9. Soak cradle bolts with PB Blaster.

10. Disconnect fuel lines and pump relay.

11. Disconnect O2 sensor. Try not to smash it into the firewall when removing engine….

12. Disconnect trans cooler.

13. Disconnect engine to chassis ground strap(s). Don’t forget this stupid thing.

14. Disconnect engine wiring harness on the engine.

15. Disconnect A/C Lines. I didn’t have to discharge it because it didn’t work anyways.

16. Wheel cherry picker over and position to lift car and engine.

17. Break lug nuts loose so they can easily be removed with wheels off ground.

18. Soak cradle bolts with guess what? more PB Blaster. You’ll begin to love this stuff later.

19. Attach chain to engine block and lift car high enough to knock florescent light down.

20. Lower car, fix light, raise car, paying more attention this time.

21. Insert jack stands under jacking points on rear of car. Wheel wells must be at least 45″ high.

22. Lower car carefully on jack stands, be sure they are stable.

23. Remove wheels and calipers, I took my brakes off entirely.

24. My park brake cable was rusted solid, so I had to cut it off.

25. Remove strut bolts.

26. Loosen front cradle bolts, but don’t remove yet.

27. Raise cherry picker just enough to support engine.

28. Remove rear cradle bolts. I got super lucky and mine didn’t spin. :D

29. Remove bolts from front mounts, and lower cradle assembly onto heavy-duty creeper.

30. Wheel engine out of right hand wheel well.

31. Miller time.

Air tools are very very handy for the cradle bolts, especially if your car is having its engine yanked out for the first time in 23 years. Above all, be smart and DO NOT work under a car supported by only the cherry picker or jack. If the Fiero falls, you WILL be crushed, there isn’t enough ground clearance to get lucky.

Engine Bay Cleaning

First of all, every Fiero owner-turned-mechanic is obliged by unwritten law to provide the “standing in the engine bay” picture upon successful removal of the engine. Here is my compliance:

Ok, time to get serious. One of the problems I had with the car was a badly rotted battery tray. Most old Fieros are going to have this problem. I had a bungee holding the battery down on the tray, which worked fine for a while. In hindsight though, it was pretty stupid since the battery sat about 2″ away from the spinning water pump pulley and belt.

So one hard corner later, guess what? The strap gave out, the battery slid into the pulley and sprayed energized hydrochloric acid all over my car’s engine compartment. nice! So needless to say, I later cleaned it out, sprayed a little paint over the bare metal to attempt to stop the rusting, and tacked in a spare battery tray out of an old Chevy truck my brother had lying around. That worked great and I was able to bolt the battery in place. But I still had a rusty mess in the engine bay.

Fast forward to today. I jumped in the engine bay and started pulling down the nasty old insulation to get at the metal.

With the old firewall insulation out of the way, I could start cleaning the engine bay out for the 4.3L to go in. What good is a swap if the engine bay looks like trash? I ground down the spot welds and removed all the old rusty remnants of the factory battery box.

I then proceeded to scotch-brite and paint the engine bay. I ground some of the old brackets off the firewall since they will no longer be needed.

That pretty much concludes the engine bay cleaning portion of the build.

Why The 4.3L V6?

I seem to get asked that question alot, so here I will go into length on the research I did regarding this engine and my own experiences.

The biggest question I hear on PFF is, “why a 4.3 when you have to do the same work to install a V8? why not just go with a SBC and get the extra 2 cylinders?” Well, here’s why. The 4.3L is lighter than the 350 Chevy, and it fits in the Fiero engine bay much nicer without having to run a goofy water pump setup. The TBI wiring is a piece of cake, and personally, I want to have some extra room in the engine bay for future forced induction possibilities. Yes, I could get more power per $ with a SBC, but again, these are MY reasons, if you don’t agree, then put something else in your car.

You can compare the dimensions of the SBC and the 4.3L V6 below:

I originally planned on installing a 4.9L Cadillac engine, as the power was phenomenal off low end and it bolted right up to the fiero trans. However, the wiring on the ’84 cars is complicated because of the issues with the C500 connector’s location, as well as being confusing overall splicing the two harnesses together if you don’t have experience with these engines.

I used to own a 1991 K1500 Chevy truck with a 4.3L engine in it. That truck was amazing, it was a full-size truck, long bed 4×4, and that little V6 with 300,000+ miles could still light the tires. Torque up the wazoo! So having plenty of experience working on that 4.3L, as well as having done a swap on that truck and dealing with the wiring of the ECM, I knew alot about how the engine would wire to the Fiero: piece of cake. You can run the 4.3L on an engine stand, just plug the harness into the ECM and give it +12v.

A brief comparison of the two engines, in their respective vehicles:


1995 GMC K1500 (year I am getting my 4.3 from)

- 4,300 cc 4.3L V6

- 4″ bore, 3.48″ stroke, 9.1 compression ratio

- Overhead valve and two valves per cylinder

- Unleaded fuel

- Fuel economy Mileage (City / Hwy) 14/19

- Throttle body injection fuel system

- Curb Weight 4517 Lbs

- Power: 160 HP @ 4,000 rpm (CPI/Vortec Heads: 190HP @ 4,400 RPM)

235 ftlb @ 2,400 rpm (CPI/Vortec Heads: 250FtLb @ 2,800 RPM)

Pro: shares many perf parts with SBC (heads, cams, intakes, turbo syclone/typhoon parts)

Con: requires adapter plate and flywheel mods

1995 Cadillac Deville

- 4,893 cc 4.9L V8

- 92 mm bore, 92 mm stroke, 9.5 compression ratio

- Overhead valve, two valves per cylinder

- Premium unleaded fuel

- Curb Weight 3756 Lbs

- Fuel economy Mileage (City / Hwy) 16/26

- Multi-point injection fuel system (PFI)

- Power: 200 HP @ 4,100 rpm

275 ftlb @ 3,000 rpm

Pro: bolts right up to fiero trans, or 4T60/E

Con: very few performance hop ups besides reground cam & porting


The ’95 Silverado (K1500) has a curb weight of 4,517 lbs, nearly twice that of the Fiero’s 2790Lb. A common rule of thumb is that every ten pounds of weight reduction is like adding 1 additional horsepower, so by that rule the Fiero will scoot as if it had an extra 173HP along with the existing 160, and anyone knows a Fiero with 333HP is going to be pretty damn quick. But enough with the shade tree math, its just a guesstimate. Obviously the same math applied to the 4.9L results in a Fiero equivalent of a 97hp boost on top of the 4.9L’s 200hp, which has the little 4.3L ahead by 36hp. Either engine will provide a nice quick Fiero!

Fuel economy is hard to figure, but seeing as that the engine is only pushing about half the weight of the donor vehicle, I am expecting something like 20/30. When I get the swap done, tuned and road tested, I’ll post my actual MPG.

I know a few TBI mods I did on the old truck I had, as well as the available cams, intakes and Vortec heads that will really wake up this little 4.3L. The TBI engines get a bad rap because of the crappy flowing pre-Vortec heads. Hot Rod magazine did a buildup of a 4.3L with ported non-vortec heads and only squeaked 300HP out of it. (they later did a 500HP supercharger on that same engine, but that’s a different story…maybe stage 5? hehehe…) I drive in the low end of the powerband, using the torque. I am a stoplight drag, 0-60 kind of Fiero Enthusiast. My engines rarely see over 4500RPM, so these torkie engines are my ideal platform.

I plan on adding 4 bolt mains to the 4.3L when I tear it down to install the cam and fresh bearings in the lower end. When my old 4.3L in the K1500 started to go, it was a bad rod bearing, so I will be pulling the engine apart to install high-quality Clevite bearings, and have the 4-bolt caps installed and the block line-honed at the same time. Seeing as that some form of forced induction may or may not be in the future, I like to have enough beef in the low end to do it.

There are FAR more performance parts available for the 4.3L than there will ever be for the 4.9L Caddy – partially because the 4.3L is 3/4 of it’s big brother 350 SBC, partially because of the 4.3L’s brief stint in the Busch Series cars. GM Performance Parts makes some nice 18° heads, and I think I recall Brodix making something as well.

So to summarize, for me and my purposes with the car, this engine is the ideal engine. Your opinions may differ, but don’t flame me saying I should just go SBC…I explained why I’m not, just read.


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