3.4L DOHC Fiero Engine Swap Guide

page 5

Now it is time for the all-important dog-bone mount, or torque strut mount.  The stock Fiero has a single dog-bone mount that ties the upper right hand side of the engine into the right strut tower and rear trunk compartment.  The 3.4 DOHC engine has NO provision for a dog-bone mount in this area, and to make matters worse, the intake manifold is so large, it leaves you little room for a mount in this location.  However, there is a structural lift bracket that does tie the rear head into the engine block in this area, which I used as a mounting point for my custom dog-bone mount bracket.

For material, I recommend using 3/16"-1/4" steel plate.  I simply mocked up a 4-cylinder dog-bone mount in the vehicle, and positioned it for the best possible clearance.  Keep in mind that I used a vacuum manifold block from a 95 Lumina 3.4 DOHC engine which does NOT have a provision for MAP sensor mounting.  Otherwise the dog-bone would interfere with the dog-bone mount.  You may also need to redrill and move up the dog-bone mount on the chassis side to gain better clearance of this manifold block, as I had to do.

Once the mount is connected to the chassis, you can lay it onto the engine and determine what you need to build to connect it to the engine.  This is what I came up with:

The other reason why I recommend you use thick steel is because you can tap threads directly into the bracket which saves space and the hassle of trying to sneak a nut into so tight areas.  This bracket design bolts to the factory lift bracket in two places using existing holes.

I suggest tack-welding the bracket together for test-fitting purposes.  Be sure to leave yourself enough clearance for the dog-bone to slide in and out of the bracket otherwise you might have a tough time getting everything together.  When you are finished, you should have a bracket that should withstand anything the 3.4 DOHC engine can throw at it.

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