Does anyone know if LT1's are internally balanced or externally? I have a 95 LT1 out of a Caprice and would like to put a 6 speed behind it. I can get the flywheel from the 6 speed car but not sure if I can just bolt it on (I know physically I can) or if I'll have to have everything rebalanced.

 

It's sort of both.

The one piece rear main seal blocks lost the extra throw on the back of the crank that the 2 pc cranks used to "final balance" the crank.

The flywheels/flexplates for the 1 pc rear cranks are the final part of the balancing process.

I would like to be able to tell you that you'll have no problem because GM should have made all the flexplates/flywheels the same. That doesn't mean they did.

I'd talk to a machinist that has experience, or even talk to a dealership if you have to.

 

The manual flywheel was from what engine? If it was am '86-later SBC, it should fit the LT1 crank.

 

well it's from the same engine the T-56 came off of, seeing as they didn't make them in '86 it's a later motor. The flywheel is from an LT1 engine. I know it will physically bolt on.

 

Then the extra "bat weight" on the flywheel should be correct for the LT1. This extra weight only compensates for the offset hub weight that would have been cast onto a two-piece rear seal crank, not for any other crankshaft imbalance. The remainder of the difference in engine balance is done with the flyweights on the crank itself.

http://www.gmgoodwrench.com/gmgoodwr...396&section=ep