Just to add a comment, the heaviest of the aftermarket (billet) flywheels I've found is 30 lbs. The heavier Mcleod billet flywheel is 27 lbs. and the lightweight 464122 we're talking about is 20-22 lbs. The OEM flywheel is cast iron and likely over 30 lbs. Surely someone here knows but I bought one 2 years ago that was an "OEM replacement" that was 35 lbs.

As to weight and rotating mass, it can work for you or against you depending on what you're trying to do. Less rotating mass obviously allows quicker RPMs but in a heavier car / taller gears that can be problematic. Pro Stock cars have traditionally added flywheel weight given they have no issue getting engine RPM and the added weight helps maintain engine RPM during launches and shifts.

- EM