Swapping a 3800 into a fiero requires a flywheel that will fit on the engine and not interfere with the transmission. There are a few ways to go about this but generally the simplest is to use a modified 3800 flywheel. These can be purchased or made from a flywheel for vin K Camaros from the early 2000s. When I bought the car, it came with a brand new Camaro flywheel so I decided to work with that.
Side note: The stock Camaro flywheel has several dowel pins around the perimeter that mate with the stock Camaro pressure plate. These need to be removed to work with the Fiero and before any machine work can be done. I had a really hard time grabbing them, and what finally worked was to thread a die onto them and use that to twist and grab them. The right size die was one a little too small–you want it to thread onto the taper at the beginning and then stop and grab. Once the die grabs you can twist (clockwise only) while pulling away from the flywheel and they should come out pretty easily.
Back to machining: Shops in Seattle didn’t seem interested in doing this job and couldn’t give me reliable estimates on the cost. As of this writing West Coast Fiero sells a pre-made flywheel for $295 which is probably at least what machine work will cost in a big city.
I have access to some facilities and expertise so I finally buckled down and removed 0.270″ of material from the friction surface of the flywheel using a large lathe. I measured the runout before I started working on it and it was about .004″. I removed the ring gear and mounted the flywheel in a 4-jaw chuck. I centered it in the check and then used a dial indicator to make sure the friction surface was running true to the cutting tool. Then I did a series of facing operations until the right amount of material was removed.
The finished thickness from the crank mounting surface to the friction surface is supposed to be 0.840″. I ended up with .830″ so I messed up somewhere. But there is some wiggle room here so it will be fine.
I’ve never machined cast iron before so that was interesting. Lots of messy chips.
The most interesting thing with the job was once I was deeper into the flywheel I exposed a number of casting flaws (pictures below. It’s not to clear to me if they will affect the clutch performance noticeably or affect strength. We’ll find out. For what it’s worth, this flywheel was made by AMS Automotive.
The flywheel needs to be rebalanced next. I’ll cover that in another post.
Now that I’m about done with this part I have a much better idea of the quality of the flywheel casting and the machining costs. Based on this information, if this wasn’t a Lemons car ($500 limit) and I hadn’t gotten the Camaro flywheel with the car, I would absolutely buy a pre-modified flywheel. With the variability in flywheel quality and machining costs, there is zero risk-adjusted savings in modifying a flywheel.