The double keyway option requires that the factory or aftermarket crankshaft be removed from the engine and a second keyway cut into the snout of the crankshaft. DO NOT run a double keyed damper on a crankshaft without the double keys. Failure to the damper hub can happen without the supporting key in the broached keyway slot. The dual keyway option is for Supercharged or Extreme Duty Applications (typically over 750 rwhp). Without the double key modification your crankshaft in these high horsepower applications can lead to the failure of the damper hub and/or the single keyway which results in damage to the damper and the crankshaft snout.
Blower Hub Option - Add $25.00
The super duty hub has increased material for supercharged applications.This increased material helps to protect the hub from cracking in high load applications. The super duty hub is recommended for supercharged applications making over 750 rwhp. Includes matching timing cover oil seal.
Exceeds SFI 18.1 standards and is marked on front with SFI Sticker, and on the rear with SFI number stamped into unit.