Motor State Distributing has set the pace for highperformance automotive components for racing, street and offroad use. Features. Piston Forged 4.040 in. Bore 0.07 x 0.07 x 0.18 in. Ring Grooves Minus 6.1 cc. Piston. Speed Pro. Forged. 4.040 in Bore. 5/64 x 5/64 x 3/16 in Ring Grooves. Minus 6.1 cc. Coated Skirt. Small Block ChevySpecifications. Size 4.040 in.