The Edelbrock 602579 small block Ford Performer RPM cylinder heads are designed exclusively for the SCCA American Sedan Series Class. They feature 1.94" intake, 1.55" exhaust valve sizes and non interlocking valve seats. To comply with class rules, there is no blending work in the intake entries, exhaust exits or bowl area of the intake or exhaust. The casting is manufactured of A356 aluminum and heat treated to T6 spec for superior quality. All heads include manganese-bronze valve guides, one-piece stainless steel valves with hardened tips, ductile iron valve seats and Heli-Coil® threaded inserts in the exhaust and rocker stud holes. Bare heads will require final sizing of the valve guides and proper valve job prior to the installation of valves. All Edelbrock SCCA RPM heads are engraved with the SCCA approved logo and are legal for the American Sedan Class. For additional information, please refer to the SCCA rule book.