GSC Power-Division

GSC Power-Division CNC Cylinder Head | 2003-2006 Mitsubishi Lancer Evolution 8/9 (GSC4508 / GSC4509)

  • Sale
  • $4,605.01
  • Regular price $5,417.65

GSC Power-Division's CNC cylinder head for the Mitsubishi Evolution is nothing less than perfection.

GSC starts with a brand new OEM Mitsubishi cylinder head that is checked for port wall thickness and for casting flaws. After a good casting is approved, the steel valve guides are removed and the cylinder head is locked in to GSC's 5-axis mill and the port work begins. Using the latest in computer aided software GSC has designed new intake and exhaust ports for the 4G63 head along with a reshaped combustion chamber to maximize port velocity and flow.

Once the CNC Mill is finished milling away the unneeded aluminum from the cylinder head, the head is removed and cleaned to remove any loose aluminum from the milling process. GSC installs a set of Bronze valve guides into the head and it's off to have a precision valve job to allow for the +1mm over intake and exhaust valves.

For the valve job GSC relies on a CNC-based Newen Contour-BB to perform precision accurate valve seats specially designed to allow for maximum velocity where it counts most, right at the valve!

After all machining is finished the cylinder head is hot tanked and pressure cleaned before it is ready for final assembly. When installing each of the black nitrated GSC stainless steel Intake and Exhaust valves proper stem height is checked on each and every valve stem. Every valve stem is ground to its OEM height to maintain exact valvetrain geometry. A matched set of GSC's PACALOY Beehive valve spring and titanium retainers are installed using GSC Viton valve seals and the exhaust and intakes are shimmed to provide seat pressures within 3% of each other. Finally, a spec card is generated and the GSC CNC Cylinder head is ready for a life of extreme performance.

Sold individually.


  • Exact tolerances and matching port dimensions across all cylinders ports
  • 35mm GSC Stainless Steel Black Nitrided Intake valves
  • 31.5mm GSC Stainless Steel Exhaust valves for the highest heat capacity
  • PACALOY Beehive valve springs for maximum performance up to 11,000 rpm
  • GSC Titanium retainer and Chromolly spring seats
  • New Bronze/Magnesium Valve Guides
  • Valve train and port velocity designed for up to 12mm of camshaft lift
  • NEWEN Valve Job
  • Each Head is pressure checked and decked
  • Sold Fully Assembled and ready for use


    • 2003-2006 Mitsubishi Lancer Evolution 8/9