I must respectfully disagree with the previous post. I put a lightweight flywheel in my 77 during a rebuild to remove 13lb of rotational intertia thus freeing up additional power. The motor revs so quickly the difference is amazing. With a centerforce II clutch there is virtually no negative side effect that I can tell. Driveability is just lik stock. I expected the clutch to be heavier but it is not.
Mine is the HKS unit which has two different materials for the best combination of lightweight and durability. I paid about $260 for it on the internt.
Is it possible to lighten the stocker?? I could throw it in the lathe at work, and even go as far as using a dividing head to bore holes in it. Has anyone done this? Mabee the balance would be affected too much?? Getting it balanced after would cost me at least 100$ (almost not worth the time involved), but mabee not necessary?? If you can machine the friction face, you should be abled to take some meat elsewhere, you'd think anyway. What is the stock weight, and what do the "lightweight" units weigh?
I've done it. I have a car with a lightened stocker right now. But that cast flywheel is an amputation waiting to happen!
Not for use if you are going to seriously abuse it, for the cost of an SFI 3.1 rated wheel!
I don't think "drivability" is sacrificed to any great extent.
I have 13 and 11# unnits in EVERYTHING, and will be putting a 9# unit in the Turbo soon, though admittedly, that one is an "occasional" driver...
The 13 and 11# units are "daily drivers" and my WIFE even complimented me on the change in the 260 after installing an 11# unit in it!
I just got mine stock flyweel lightened by Nathan Gerolomy in Sac. Went from 20.5 to 16.6. That's about all he would do for safety's sake.. cost 150.00.
Let's do the math.... $150.00 / 4 lbs = $37.50 per pound... I dunno - I think I should have went out and bought an aluminum flywheel.....