lt1form

Just like the title says, Do you guys know if a lightweight flywheel would throw the balance of the motor off ( cause any vibration )????

Or a smaller underdrive pulley???

Injuneer

The flywheel has to be "specific" to the LT1, which is externally balanced, using a weight on the flywheel. As long as the light weight flywheel is for an LT1, with the weight on it, you will be fine.

The damper/pulley is just that.... a harmonic damper. It is not a balancer, and is neutral balanced. Changing the diameter of the damper/pulley will not change the balance.

lt1form

Thanks, Injuneer!

So can you install a lightweight flywheel on an existing stock motor, or does it have to be balanced at the machine shop with the entire rotating assembly?

DjArcadian

I had one installed and ever since I"ve had a slight vibration. After getting some new motor mounts and the harmonic balancer re-adjusted most of the vibration went away but much of it was still there which I believe is a result of my Star Spec flywheel. I'm not 100% sure as vibration can be caused by a number of things. I later put in a poly tranny mount which increased my vibrations a bit but after a few weeks they settled back down as the mount broke itself in.

WayneE

When I put in my Street Twin, I had the flywheel imbalance matched to my stock flywheel. It was very smooth. Then when I rebuilt my motor, I had it neutral balanced.

IMO if you're replacing your flywheel on a stock motor, take the new and old to a machine shop and have them get the balance the same.

lt1form

Thanks guys!