I have had an aluminum flywheel in my car for a while now and never had it balanced correctly when installed and was getting a lot of vibrations. I adjusted the damper/harmonic balancer because I knew it was off, had a poly tranny mount and had a cutout so I factored in my vibrations as involving all these things.

Well, I got the aluminum flywheel pulled today and the old steel one installed again and it's a whole new car. No vibrations AT ALL even with the poly mount and cutout. I was thinking of selling the car but no way I'm selling it now.

The flywheel is still good but needs to be balanced correctly with the old flywheel. This was my mistake when I got it installed. I didn't get it balanced matched with the steel stock flywheel. I'm gonna sell it in the for sale section if anyone is interested.

 

Just curious, what do you mean "balanced matched with the steel stock flywheel?" I thought if it was balanced, it was balanced.

 

In most SBC engines an evenly balanced flywheel will work because the engine is balanced internally between the two main crank bolt down areas. BUT LT1's are externally balanced meaning that the flywheel is heavier in some areas than others, or that the weight is distributed unevenly. I found this out the hard way when I put a 383 flywheel on my stock LT1. **** it felt like I had about 700hp the car shook so much. Needless to say I took it off right away and put the stock flywheel back on.

 

That's a standard procedure for any clutch/flywheel change. You should always balance new stuff to the existing stuff.

Balance matched means you are taking the new flywheel and balancing it to the same specs as the old one.

To me, thats cutting a major corner. As you found out it is Thats like assuming that a rotating assembly is balanced from the manufacturer and then having to tear the whole motor (transmission in your case) apart to fix it.

But good thing you leanred something from it!

 

The real problem was that I got the flywheel from somone else and and he said it was for a LT1. But what he also didn't say was that his LT1 was a 383. He had just bought a new PP, flywheel and clutch package. The old set up hadn't even been used for 2k, So I figured that I could pick up a newer, lighter flywheel for cheap, since he wasn't gonna use it.