LT1 flywheel balance problems

A couple months ago I had a shop install a Spec steel flywheel and a RAM HDX clutch kit in my stock bottom end LT1. The car came back with some vibrations at 1800 and then at 2800 on up. Not liking the heavy flywheel and wanting to address the vibe problems I decided to switch to a Fidanza aluminum fw. In the first swap the Spec was not match balanced to the original flywheel, which unfortunately is now long gone. The Fidanza was installed as-is with the 125g counterweight in place. As you can probably guess, it still has bad vibrations. I have the Valeo pressure plate which has been drilled from the factory for balancing, so that probably isn't the problem.

Am I outta luck with balancing the LT1? Is it now a vibrating brick for the rest of its (short) life?

Same issue as you bro. New Clutch new Flywheel bad Vib.


Old Flywheel had a weight on the back and the one we put in didnt have any sorta weight on it. I have been told to try taking the bolts out of pressure plate turn the pressure plate 180 degrees and bolt it back up. Let me know if you figure something out the bad Vib is making me crazy as well.

If you have a stock bottom end, you'll need the counterweight which is approx 125g. OTOH, most built engines are internally balanced and use a zero-balanced flywheel. While some of the cheap pressure plates on the market today might be up to 20g out of balance, which is really bad, changing its orientation on your flywheel probably won't compensate for the 125g needed to balance the back half of the crank assy. There are a couple of very good threads on this.

Not having an original flywheel on which to base a new fw installation might be a real problem. I have a few of ideas in mind. 1) Get a cast fw from Autozone and try it. This would probably still need to be balanced against my original. 2) Have the Fidanza zero balanced without the counterweight and then put the weight back on. Can the Fidanza be off by that much? 3) Try different orientations of the pressure plate.

Question for the forum: does each LT1 get its own unique flywheel at the factory? If so, am I screwed?

If you have a stock bottom end, you'll need the counterweight which is approx 125g. OTOH, most built engines are internally balanced and use a zero-balanced flywheel. While some of the cheap pressure plates on the market today might be up to 20g out of balance, which is really bad, changing its orientation on your flywheel probably won't compensate for the 125g needed to balance the back half of the crank assy. There are a couple of very good threads on this.

Not having an original flywheel on which to base a new fw installation might be a real problem. I have a few of ideas in mind. 1) Get a cast fw from Autozone and try it. This would probably still need to be balanced against my original. 2) Have the Fidanza zero balanced without the counterweight and then put the weight back on. Can the Fidanza be off by that much? 3) Try different orientations of the pressure plate.

Question for the forum: does each LT1 get its own unique flywheel at the factory? If so, am I screwed?

No, they are not individually balanced. I kind of got lost in the whole story, but if your rotating assy. is stock, a stock balance flywheel will be awfully close - close enough as not to cause significant vibration anayway.

Rich