Fiero 4.3L-v6

Fiero 4.3L-v6 by Steve

I found this during a search on the web at I did not copy the entire article because there was not enough about the mod for the brakes and I was just interested in the 4.3L swap.

Anyway I don’t the last name but this article is by Steve.

The engine swap, I used a partial v8Archie kit. I didn’t want the extra weight, heat, or cutting required for a v8. I bought a front motor mount “U” plate, crank flange adapter, and a block adapter for $610 from Archie. I also needed a remote oil filter system and gear reduction starter with multiple mounting positions. I made the mistake of buying a kit for a automatic instead of a manual and there are many differences. On the phone, Archie isn’t one to volunteer much information although he has been quick to correct my terminology and let me know it’s been a long time since I bought the kit. My kit required cutting the bellhousing for starter gear clearance and retapping the crank flange adapter for fine thread flywheel bolts instead of coarse thread auto flexplate bolts. Feel free to email me if you have questions.

Here is a finished and running pic except for the air cleaner which there is very little room for(my next undertaking). While it’s easier and convenient to solid mount the engine like Archie does than to use a rubber mount, it’s also a bad idea for a number of reasons. Many an old hotrodder can tell you what happens if you solid mount an engine and leave a rubber trans mount. The trouble with rubber mounting is the factory mount is too far rear ward. It’s not centered under the crank. The dogbone or torque rod would be under stress all the time. While keeping the engine in the same position, I have since moved the rubber mount as far forward as possible and added two rod ends with a short tube between them bolted at one end to the V block and the other to a piece of angle bolted to the cradle just ahead of the mount. This supports the engine while letting it move on the rubber. A torque rod is still used at the rear but it only has to deal with engine torque now, as it would with Archie’s typical v8 engine mounting.

Here you can see the reason for running a 4.3L instead of a sbc. The forward valve cover clears the hinge box nicely with no cutting. The water pump pulley also clears easily. I rolled the frame lip down for extra clearance. It about 2″ between the pulley and frame rail. I didn’t move the transmission out of the stock location or extend the trans mount adjustment slots as Archie suggests for the v8′s.

In a nut shell, to put a 4.3L in a fiero you need the following. Archie block adapter, crank adapter, and front engine mount($610). Gear reduction starter with multiple mounting positions($150). Remote oil filter mount($12), 24″ hoses($20), Canton racing products bolt on oil filter bypass with 18mm thread($60), an extra driver side manifold($20), a complete 1985-present 4.3L v6, short water pump for small block chevy(sbc), low mount alternator bracket for driver side for sbc($25), single groove pulley set for sbc with short water pump($45), a sbc right hand or straight water neck($7) and remote Moroso water filler($25) or a water neck filler($55). Various cushioned clamps(addel) to support hoses($?aircraft supply). Water pump inlet=1 3/4″. SBC water neck=1 1/2″. Fiero rocker pipes=1 1/4″.

Two s10/astrovan driver-side exhaust manifolds with 3 inches of exhaust pipe are required along with one 2 inch 180 degree mandrel bent pipe($12 from JCWhitney). A s10/astro passenger-side manifold won’t clear the speed sensor on the transmission and fullsize pickup 4.3L manifolds are different. I reused the stock exhaust after the Y pipe, adding a T for the rear manifold using half the 180. The other half was used at the rear.

A filter bypass is why the starter isn’t in the stock location, necessitating bellhousing modification. I bought 3 oil filter bypasses before I got one that would clear the mini-starter. The first one($20) on the left would have cleared but the output ports overhang the filter base area. The 4.3L has a recessed filter pad and an 18mm thread. The second one($9) fits but there isn’t enough room for elbow fittings. The last one from ($55) worked perfectly. They make lots of cool stuff.

I used a remote filter for a ford filter because it was (A)$12 versus $40 for a GM thread and (B) I had it laying around. I mounted the filter vertical instead of side ways like Archie does it so I will have more capacity and it’s less messy to change. The bracket is just Home Depot 2×2 angle secured with 2 3/8′s bolts. Thats a bolt on heat shield from 2024-O I made for the alternator and around the pipe near the starter(gets very close)Theres also a aluminized, ceramic blanket around the starter left over from another project. You can almost make out the lower rod end that supports the engine near the alt heat shield described below.


1 comment to Fiero 4.3L-v6

  • ponchogeezer


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