Cosworth CNC Big Port Head Castings Dual AVCS (08+ STi)

Item # 20004544
$4,425.00 MSRP $4,463.00

Cosworth Big Valve Cylinder heads for the Dual AVCS 2008 STI EJ257B engine. Machine Ported for maximum accuracy and performance, complete with larger (+1mm) valves and dual valve springs for maximum flow. Cosworth Big Valve Cylinder heads are the key to high power and unlocking the performance potential in your Subaru engine.

  • CNC Ported/Machined finish port
  • New Castings
  • Hand blended finish work 
  • Intake 13.63% (average) 19.38% (max) increased flow
  • Exhaust 31.44%(average) 37.78% (max) increased flow
  • 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