Muscle Head Stage IV: Program V1-P1-F12, 2.550″ x 1.975″ valve dia. 103cc chambers. Std Copper intake valve seats, B5 Exhaust valve seats, .018″ Jr Hoops & All 9/16″ Head stud inserts. 2.00″ lifter spread, 12* Exhaust Flange.(pair)

Muscle Head Stage V: Program V2-P8-F12, 2.490″ x 2.020″ valve dia, 104cc chambers. Std Copper intake valve seats, B5 Exhaust valve seats, .025″ Jr Hoops & All 9/16″ Head stud inserts. 2.600″ lifter spread, 12ø Exhaust Flange. (pair)