I'm getting a pretty noticable vibration at various RPMs. Usually right around 1200-2000, and then again at anything over 4000. The vibration is present if i simply rev the engine at a stop. I don't have to be in gear. I just swapped in a T56, and I'm wondering if the flywheel is out of balance? The flywheel is used, but it has been resurfaced, and on the back you can see where they drilled some divots, so I'm assuming they balanced it or attempted to. I'm also wondering if it could be a missfire or a dead cylinder. I'm not sure that all my injectors are working up to par. I checked the spark plug wires to make sure theyre all going to the correct cylinder. Any ideas? The motor is a stock L98.

 

Actually, the vibration is pretty bad at 1000 rpm. I've read that you're supposed to line up the pressure plate a certain way on the flywheel, but I have a stock LT1 flywheel that I got with the trans and there are no marks on it. So even if i wanted to line them up i wouldn't be able to.

 

Does the new flywheel have the balance pad like the old stock flexplate did?

 

I don't think it did, but it had spots where there were drill marks where they removed material. I'm assuming this was for balancing purposes.

 

At the crank flange, there should be 6 bolt holes and an index hole. Use that index hole to reference the balance pad on a stocker, and the holes in your new flywheel should be exactly opposite. Be sure both are turned crank-side towards you.