The Ultimate High Performance Head. Featuring Cosworth Ports That Flow 95% Of What A Perfect 42Mm Tube Will Flow On A Flow Bench. Fully Machined Combustion Chamber, No Special Exhaust Needed, Chevy Size Springs. Available In 92Mm Or 94Mm Bore In 42Mm X 37.5Mm Or 44Mm X 37.5Mm Valves. These Come Complete With Stainless Valves, Chevy Dual Springs, Chromoly Retainers, Hardened Keepers And Polished Valve Covers. 48Mm X 37.5Mm Valves Available In 94Mm Bore For Additional Charge. Sold As A Pair