IAG 1150 CNC Ported Drag S20 Cylinder Heads Package (No Cams / Lifters) For 02-05 WRX

The IAG 1150 CNC Ported Drag Cylinder Heads are designed for drag racing and competition. These fully CNC ported heads provide a significant upgrade in long term performance over the IAG 950 heads. These heads work great for cars where getting the most power with maximum reliability is the goal. The IAG 1150 heads are the best heads available for high-horsepower drag racing. They are designed to support up to 1150 BHP with supporting mods. These heads include upgraded Ferrea Valves, GSC Viton Valve Stem Seals, Upgraded GSC Valve Guides, Ferrea Dual Drag Valve Springs with Titanium Retainers, and Ferrea Keepers. GSC S2 or S3 Camshafts are available with Kelford DLC Coated 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 1150 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 S2 or S3 Camshafts and Kelford DLC Coated Lifter Buckets for valve adjustment.

This IAG 1150 fully CNC ported head package starts with brand new WRX STI OEM head castings directly from Subaru of America. The bare castings are visually inspected then fixtured into our in-house Centroid 5-axis CNC Machine. The Centroid CNC ports the intake and hard to reach exhaust "dog-leg" port runner. The benefit of CNC porting is not only an efficient way of machining the heads it also offers consistent port results that are hard to achieve by hand. Once the Centroid completes the port process the heads undergo a cam clearance machining process that removes material from the lifter area where large duration cam profiles are known to contact the castings. Shortly after the heads are drilled to fit larger 1/2" or 14mm head studs, which are commonly used in high horsepower builds. Next, the OEM guides are pressed out and replaced in favor of GSC Manganese-Bronze valve guides that are shaped to improve airflow. Once all the new intake and exhaust guides are in place they are diamond-honed in our honing station. 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 Ferrea's +1mm 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 Ferrea Drag Springs and Retainers along with Ferrea Viton stem seals.

Cylinder head porting has been around since the invention of the internal combustion engine. It can be done by hand with a die grinder and some cartridge rolls, and a seasoned professional can likely get a good result that way. Unfortunately, doing porting this way requires a lot of experience and care. One slip of the die grinder can ruin your cylinder head. This is where CNC porting comes in. Using our Centroid 5 axis CNC porting machine we can achieve the same results every time we put a set of heads into the machine. Every cylinder head comes out exactly the same and uses our race-proven, computer controlled, CNC porting program to guarantee results.

To get the most out of these heads you'll want to select the GSC Power-Division billet S2 camshafts for your IAG 1150 Head Package. These cams are built to suit the higher horsepower these heads will support. With a power range of 500 WHP and up, you need some additional supporting mods to utilize the true potential of the S2s. Our IAG 1150 Short Block, an upgraded turbocharger and fuel system, and a quality engine management system are key.

If you're targeting maximum power over 1000 whp and willing to give up some low end drivability, the GSC S3 cams are the way to go. Along with the camshafts we'll include all new Kelford DLC Coated 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.