These heads are designed for the SPEC racing classes looking for conformity amongst competitors. AFR's reasonably priced 210cc intake port SPEC heads for small block Chevy are the only true out of the box SPEC heads available. They require no additional work and truly meet the meaning of affordable racing that is the intent of SPEC components. Our Race Ready version comes with 100% CNC ported intakes and exhaust ports and CNC ported 66cc combustion chambers. AFR's 3/4 thick head deck makes them extremely durable and dependable for circle track racing so that you finish what you start. Standard valves are 2.080 intake and 1.600 exhaust with AFR's hardened ductile iron interlocking valve seats. The exceptional flow characteristics, 23° valve angle, and standard valve spacing make this the perfect head for 350 to 400 cid engines operating between 3000 and 8500 rpm. No special parts are required. Dual valve cover bolt pattern is standard. Chevrolet Small Block - 210cc Spec Racing Head - 65cc Combustion Chambers, Angle Plug - Bare Heads