Cosworth CNC ported cylinder heads feature dyno tested and flow bench proven ports, engineered for maximum usable power. Each new cylinder head is ported on a 5 axis machine to ensure consistency and perfect port shape every time. Additionally, larger intake (+1mm) and exhaust valves (+1mm) are utilized to help increase flow. Cosworth CNC ported Big Valve cylinder heads come complete with a performance valve job, hi rev (max 10,500rpm) valve springs with titanium retainers and are ready to install. Perfect for high performance applications and designed for excellent torque and turbo response.