Here is the rule from the NHRA Rulebook, 2012. This rule applies to E.T. Handicap Racing, which is the type of class that 99% of the guys who drive in off the street will be in. This is bracket racing, so speed and E.T. are unimportant. Only thing that matters is cutting a good light and running on your dial-in. 11.50 and slower E.T. can use stock pieces, but you have to ask yourself, what are your feet and legs worth? I was standing in the starter box on the starting line at Firebird when an early Mustang fragged a stock, cast iron flywheel. It nearly cut the car in half. The flywheel busted into 3 pieces and the one that came through the cowl went several hundred feet in the air, then came down and landed just a few feet from the fuel trailer, which was in the pits, maybe 100 yards from the starting line.
If I remember correctly, a small piece went through the side of the driver's shoe, but did not injure him.
CLUTCH, FLYWHEEL, FLYWHEEL SHIELD
Flywheel and clutch meeting SFI Spec 1.1 or 1.2 (two-disc
maximum) mandatory on any car running 11.49 (*7.35 in the 1/8 mile) or quicker.
Flywheel shield meeting SFI Spec 6.1, 6.2, 6.3, or 9.1 mandatory
on all cars running 11.49 (*7.35 in the 1/8 mile) or quicker. Cars with rotary
engines running 11.49 (*7.35 in the 1/8 mile) or quicker must be equipped with a
flywheel shield made of 1/4-inch-minimum-thickness steel plate
surrounding the bellhousing 360 degrees. See General Regulations
2:3, 2:5, 2:6, 2:10.
