IAG 750 CNC Pocket Ported W25 Competition Cylinder Heads Package (No Cams & Lifters) For 08-18 STI

The IAG 750 CNC Pocket Ported Competition Cylinder Heads are designed with the weekend racer in mind. These CNC pocket ported heads provide a significant upgrade in flow over the IAG 550 heads. These heads work great for cars with some race track duty (road, rally, auto-x, drag) and are designed to support up to 750 BHP with supporting mods. These heads include upgraded GSC Standard Size Valves, GSC Viton Valve Stem Seals, IAG Stage 1 Valve Springs with Titanium Retainers, and OEM Keepers. GSC S1 Camshafts are available with OEM valve lifter buckets. We also offer an optional chamber modification service (see below) for EJ20 heads to allow use on EJ25 short blocks.

Each IAG 750 Cylinder Head Set starts with new OEM castings from Subaru of America. The first step is to select your Year and Model of vehicle so that we may provide you with the right castings to fit your project. Next, you'll select whether or not you want to include our optional GSC camshaft package. If selected, these heads will include new GSC S1 Camshafts and OEM Lifter Buckets for valve adjustment.

The bare castings are visually inspected and then fixtured into our in-house Centroid 5-axis CNC Machine. The Centroid CNC ports the intake and exhaust runners under the valves and blends them to the valve seat. Once the Centroid completes the port process, the heads undergo a cam clearance machining process which removes material from the lifter area where larger lift and duration cam profiles are known to contact the castings. The heads are then fixtured in our Newen Valve Guide and Seat Machine to cut all intake and exhaust seats with a multi-angle valve job that suits the flow characteristics of GSC's standard size valves. At this point, the heads' decks are resurfaced using our TS-3000 BlockMate, which cuts the aluminum to a smooth, even finish. Next, the heads are ultrasonically cleaned to remove debris and oils from the machining process. Finally, the heads are reassembled using IAG Stage 1 Single Valve Springs and Titanium Retainers along with GSC Viton stem seals.

Pocket porting is enlarging and blending the area under the valve seat. This is one of the most critical areas to get right in any porting job. Luckily, our Centroid 5 axis cylinder head porting machine gets it perfect every time. The area about 1" under the valve is enlarged and blended to ensure a smooth transition and increase power. The rest of the port is left alone because additional volume is not required at these power levels, and can even hurt velocity if there's not enough airflow.

If you're planning for more power you'll want to select these GSC Power-Division billet S1 camshafts for your IAG 750 Head Package. These will not drop any low end power, and will create more power and torque across the entire RPM range. These are perfect for stock frame upgraded turbos or up to higher horsepower upgrades. Along with the camshafts we'll include all new OEM valve lifter buckets and set bench lash using our specially designed fixture. (FINAL LASH SHOULD BE CHECKED AND ADJUSTED ONCE HEADS ARE INSTALLED)

IAG's optional Chamber Modification Service is designed to reshape the combustion chamber of your cylinder heads to closely match the chamber of USDM STI cylinder heads to allow for use with 2.5L short blocks. This service is exclusive to USDM EJ20 2002-2005 WRX Cylinder Heads. IF YOU ARE NOT USING USDM HEADS ON A 2.5L EJ25 BLOCK, YOU DO NOT NEED THIS SERVICE.