The Edelbrock #60589 Performer RPM cylinder head is designed for outstanding performance gains in 1962-79 389-455 c.i.d. Pontiac engines. They are patterned after the 1969-70 Ram Air IV Pontiac cylinder head. The Edelbrock #60589 Performer RPM head with the 72cc combustion chamber are for higher compression engines. Performer RPM head is perfect for street performance, daily drivers, street rods and muscle cars where seat-of-the-pants performance is needed. This cylinder head delivers great throttle response and power from 1500 to 6500 rpm. They also feature the highest quality intake and exhaust valves and valve springs.