Performer RPM Buick Designed for 400, 430 and 455 c.i.d. Buick engines, these Performer RPM cylinder heads are available fully assembled and ready to bolt on or bare for use with your own valve train components. Features include high-quality stainless steel 2.125" intake and 1.75" exhaust valves, 68cc combustion chambers and high flow 215cc intake and 130cc exhaust ports. Intake and exhaust runners are hand blended in the bowl area and the intake entries and exhaust exits are cnc profiled for increased air-flow. These heads include adjustable rocker stud and guide plate set-up for use with small-block Chevy 1.6:1 style adjustable rockers. The casting is manufactured of A356 aluminum and heat treated to T6 spec for superior quality. An extra-thick 5/8" deck and Heli-coil threaded inserts offer improved durability. Made in USA.