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Home » Subaru WRX/STI » Engines & Components » Cylinder Heads   Cosworth - Subaru EJ25 (STI) CNC Ported Big Valve Cylinder Heads Cosworth CNC ported cylinder heads feature dyno tested and flow bench proven ports, engineered for maximum real world 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 big turbo applications. Subaru heads are priced for the pair. A flow chart for the head is available by downloading the technical document on the left. Specification: CNC Ported/machine finished ports - New OE Castings Hand blended finish work Intake ??? 22% Increased Flow (max) Exhaust ??? 41% Increased Flow (max) 4-angle Inlet Valve job 3-angle & radiused Exhaust Valve job Valves are lapped Back-Cut Inlet Valves Heads are Ultra Sonic cleaned prior to assembly Heads are Serialized and sport a machined Cosworth logo +1mm Stainless Steel Intake Valves (1800 degrees max.) +1mm Inconel Exhaust Valves (2400 degrees max.) Performance Valve Springs Titanium Retainers Hardened Steel Spring Platforms Knife Edge port divider   Camshafts Please Select...w/out Cosworth Camshafts Installed w/ Cosworth Camshafts Installed (+$1,600.00)   Price: $4,199.00