Performer RPM CNC cylinder heads have the same specifications as Edelbrock’s Performer RPM cylinder heads for 1962-79 455 c.i.d. Pontiac engines, but feature a revised CNC machined combustion chamber design with an all-new spark plug location for improved performance. Performer RPM CNC cylinder heads are available in two chamber sizes. The 87cc chamber version is ideal for 9.5:1 engines and will deliver excellent street performance on low octane fuel. Performer RPM CNC cylinder heads with 72cc chambers are best for higher compression engines. Both are patterned after the same port flange configuration as the 1969-1970 Ram Air IV Pontiac cylinder head.