Dman65

I have a steel centerforce flywheel that is for converting a 2bolt main sbc to a '93-'97 t56. I am about to purchase a rotating assembly to build a 2bolt sbc 383 and I need to know if this flywheel is balanced externally or internally. The only number I can find on the flywheel is the 4425991 Patent number on the engine side. On the outer edge near the teeth, there are 6 large holes drilled near each other. Is this considered internal balancing? There is no weight or plate fixed to the flywheel everywhere, which leads me to believe that it is NOT externally balanced. Also, what is the difference between internally balanced and neutrally balanced? Once I know what flywheel I have, I can buy the correct rotating assembly to build my motor. Thanks for your time.

BALLSS

typically a 383 rotating assembly would be balanced "neutral"...aka "zero" balance. You would then get a neutral balance FW (this would not have a weight on the back side of it)

I would encourage you to take any FW you have to a machine shop along with your PP and have first the FW zero balanced (confirmed that it is) and then the PP is bolted to it and that is zero balanced if you are building a "internal" balanced motor

stock motor would be external (rear) balanced (weight on FW). typically rebuilt 383 motors are "internal" aka "neutral" balanced