These cylinder heads are 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. Performer heads #60579/#60575 are 50-state emissions legal for 1965-79 vehicles. They feature 87cc combustion chambers designed to maximize performance while using less expensive, low-octane fuel with a streetable 9.5:1 compression ratio. Our Performer RPM heads with the 72cc combustion chamber are for higher compression engines. Performer RPM #60509 is semi-machined and must be finished by a professional head porter. They includes valve guides and seats installed with no intake pushrod holes. Performer RPM #60587 is not port matched or bowl blended and is NHRA accepted for Stock & Super Stock. Edelbrock Performer RPM Pontiac Cylinder Head 60579 Chamber Size 87cc - Complete - Single - 65-79 Pontiac 389-455 - Street LegalFor Professional Cylinder Head Porter72cc Chamber SizeAs-Cast Casting Has Small Ports And ChambersMax Valve Size is 2.11 Int and 1.66 Exh14-Degree Valve AngleEnough Wall Thickness For CNC MachiningSeats and Manganese-Bronze Guides IncludedPit Stop USAoffers Edelbrock Performer RPM Pontiac Cylinder Head 60579 at low everyday prices. Be sure to check out all of the products from Edelbrock including Edelbrock Engine Parts and Accessories, Edelbrock Cylinder Heads, Edelbrock Aluminum Cylinder Heads - Pontiac.