Muscle Head Stage II: Spread Lifter NHRA legal Pro Mod. Program #03AXSL, 2.400" x 1.900" valve dia with 55* seat angles, 96cc chambers. Std Copper intake valve seats, B5 Exhaust valve seats, .025" Jr hoops, 9/16" Top Row & 1/2" Bottom Row head stud inserts.(2.600" lifter spread)(pair)