hdominic

Hey guys,
I am going to try and be as detailed as I can to help you guys help me!
I am rebuilding my 1994 Pontiac Trans AM, I pulled the original engine out and will be putting money/time in it over the next months (I'm a college student, so both time and money are scarce!). So in the meantime, I opted to purchase a used LT1 engine with low miles and use it temporarily. I was under the impression that it was from a Camaro Z28 with less than 100,000 miles, but after an inspection before putting the engine in my car, it looked as though it was just rebuilt.

So, I was happy and put the engine in my car. But while I had my sub-frame out from under the car, I went ahead and replaced my suspension parts (bushings, ball joints, etc.). I used polyurethane bushings instead of stock rubber for all my suspension as well as engine and trans mounts.

Now my issue: I just drove it for the first time (I got my front end aligned) yesterday. As I drove it, I felt some weird vibrations. I realize since I didn't use rubber mounts/bushings that I would feel a good bit more shaking, but I think it is more than it should be. Especially right around 1,500 RPM (and when I punch it WOT over 2,300 RPM).

The other issue I am having with my car is it feels less powerful than it did with my old engine. The engine Revs quickly, and sounds/runs great. However, it shifts a little odd and acceleration is a lot slower. Since the engine was in fact rebuilt, I am not sure if it is a stock camshaft or not. But if it is an aftermarket cam, it doesn't seem to be much more aggressive sounding/performing than stock. But would it maybe require a different torque converter and that is the reason for the lack of acceleration? I'm running a stock torque converter.

Any ideas here, or opinions from people running polyurethane mounts would be great. I have not driven a car besides rubber mounts, so I might be reacting to nothing.

Specs on my car for reference,
1994 Pontiac Trans AM
LT1 350 Engine, MSD Coil and Opti.
Flowmaster Cat Back Exhaust (still running stock manifolds)
4L60E Transmission, stock converter.

Thanks everyone for reading this, and I hope you can give insight into my problem (or lack thereof).

Injuneer

Hard to understand if you feel the suspension is vibrating, or the motor mounts (poly?). How stable is the engine - misfires, irregular idle, etc????

In any case, not exactly "Advanced Tech" so I'll move it to a different forum.