Cosworth CNC Big Port Head Castings (04-06 STi)

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.  KK3670 is designed to fit 2004-2006 WRX STI EJ25 (2.5L) North American spec vehicles.

• CNC Ported/Machined finish port
• New Castings
• Hand blended finish work 
• Intake 13.02% (average) 20.26% (max) increased flow over stock 05 casting
• Exhaust 36.62%(average) 48.98% (max) increased flow over stock 05 casting
• 4-angle Inlet Valve job
• 3-angle & radius 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 edged ports