3.4L DOHC Fiero Engine Swap Guide
To simplify this swap guide, I have taken excerpts of the swap thread I documented over on Pennock's Fiero Forum. You can access that thread here. If that thread gets archived, you can search the archives on PFF for the title: Project 3.4 TDC / 4-speed muncie swap underway...
Before I begin, allow me to give you some history on this vehicle. This vehicle was purchased by a friend of mine and brought to me to have an engine swap done on it. It is a 1986 Fiero GT that originally had a 2.8L V6 MFI engine and 4-speed manual transaxle in it. The stock 2.8L engine had a cracked block so it needed to be changed anyway. There were also quite a few other issues this particular vehicle had that I addressed in the PFF thread but I will not go into them here.
To start off, you need to remove the engine from the vehicle. I recommend also removing the transmission along with the engine thus to simplify the cleaning process of the engine compartment and cradle. For the swap, you are going to need the stock 2.8L V6 engine computer harness and vehicle engine harness, both of which can remain in the vehicle. Both of these harnesses will be getting modified/shortened later but for now you can lay them aside.
Before removing the engine/transmission from the car, you will need to remove or disconnect:
Wiring harness from engine
Cooling system hoses from engine
A/C lines from engine and vehicle (if applicable)
CV drive axles from vehicle
Throttle cable, cruise control cable, and shift cables from engine
Ground and power cables
Fuel lines from engine
Air induction system
Clutch slave cylinder from transmission
any other vacuum lines, hoses, and wiring that still may be attached
The easiest way to remove the engine and transmission from the vehicle is by dropping the cradle out of the bottom of the car. The can be accomplished by use of a 2-post vehicle lift, or an engine crane and lift chain/bar attached to the strut towers.
Regardless of lifting method, I strongly recommend a secondary vehicle support such as jackstands once the vehicle is in the air. Typically, I would unbolt the cradle and support it by jackstands while lifting the vehicle just high enough to clear the cradle and powertrain assembly. Once the vehicle is high enough, you can support it by jackstands or similar load bearing device. Once the vehicle is in the air, you can slide the cradle and powertrain assembly out from underneath the car.
Once the powertrain/cradle assembly as out of the way, you can lower the car back down and proceed to cleaning the engine compartment and making modifications for the engine swap. The biggest modification that needs to be done to the engine compartment to clear the 3.4 DOHC engine is the notching of the right decklid hinge. Here is an example of how much material needs to be removed:
You will also need to remove the lid support spring that lifts the right side of the decklid to clear the 3.4 DOHC engine. Once this spring is removed from the vehicle, the remaining spring will no longer have enough strength to hold up the lid so you will need to add a secondary support. I chose to use a hood lift strut from a 90's Bonneville. You can use just about any lift strut for this application or buy a kit from an aftermarket Fiero parts supplier. Here are some pictures of what I did:
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