The Edelbrock #61099 Performer RPM cylinder heads are a bolt-on performance upgrade for 2003-Present Gen III HEMI® Early 5.7L engines. It's designed to fit with the stock intake manifold, exhaust manifold, valve cover, rockers, spark plugs and accessories, as well as Hellcat components. These cylinder heads have been machined to be used on either the driver or passenger side of the block. They are cast from A356 aluminum and heat treated to T6 specifications, machined and assembled at Edelbrock's facility in Torrance, California for guaranteed quality. The Edelbrock #61099 Performer RPM cylinder heads feature fully CNC machined combustion chambers along with CNC profiled bowls and port entries/exits for improved air flow. They also feature more material in the deck and reinforced combustion chambers for increased cylinder pressures. The rocker bosses have been reinforced for improved stability and strength. Extra material has been added around the intake and exhaust ports to allow for porting in racing applications. Both the intake and exhaust port flanges have remained in the factory location for use with OEM components. The intake and exhaust valves have been tipped away from bore wall to unshroud the larger valves, while maintaining factory geometry. The seat diameters have also been increased for improved heat transfer and durability over stock. Match with an Edelbrock Victor EFI #7179 intake manifold for the ultimate in Edelbrock Gen III HEMI performance.