4340 Forged steel crankshaft4340 Forged steel H-Beam connecting rods with 7/16? ARP 8740 or optional ARP 2000 cap screws2618 Forged aluminum Platinum Series pistons with Premium Chrome Moly wrist pinsHorsepower range is 900 with the ARP 8740 and 1,500 with the optional ARP 2000 cap screws