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IAG Stage 4 AW20 Ported Cylinder Head Package (Cams / Rockers / Lash Caps Sold Seperately) - 15-19 WRX

IAG's Stage 4 Cylinder Head Package for the 2015-19 WRX utilizes a CNC porting program for the AW20 heads which was developed over the past year and tested on the most successful high-horsepower Subaru's.

The ported head package starts with brand new AW20 WRX OEM head castings directly from Subaru of America. The bare castings are visually inspected and the OEM guides are pressed out. The heads are then fixtured into our in-house Centroid 5-axis CNC Machine, one of the most advanced precision engine machining equipment in the world. 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 porting process the heads are drilled to fit larger 1/2" or 14mm head studs which are commonly used in high horsepower builds. Next, the OEM press-fit freeze plugs are removed, to avoid a common known failure in which they loosen and leak coolant into the engine oil as well as externally. To eliminate this problem each head is tapped and threaded plugs are installed. At this point, GSC Manganese-Bronze valve guides that are shaped to improve airflow are pressed into place then all the new intake and exhaust guides are diamond-honed in our honing station. The heads are then fixtured in our Serdi 3.0 Valve Guide and Seat Machine to cut all intake and exhaust seat with multi-angle valve job that suits the flow characteristics of GSC's +1mm valves. The heads decks are then resurfaced using our TS-3000 BlockMate that cuts the aluminum to a smooth even finish. To remove debris and oils from the machining process, the heads are ultrasonically cleaned. Finally, the heads are reassembled using GSC Dual Cylindrical Valve Springs and Retainers along with GSC Viton stem seals.

Stage 4 Ported Head Package Includes:

  • (x2) Brand New Subaru OEM AW20 FA20 WRX DIT Cylinder Head Castings
  • (x8) GSC 35mm (+1mm) Intake Valves
  • (x8) GSC 30mm (+1mm) SuperAlloy Exhaust Valves
  • (x16) GSC Dual Cylindrical Valve Springs & Retainers
  • (x16) GSC Manganese-Bronze Valve Guides
  • (x16) GSC Valve Stem Seals
  • IAG Performance CNC Porting
  • Multi-Angle Valve Job
  • Drilling for compatibility with ½” or 14mm Head Studs
  • Threaded Coolant Plug Upgrade
  • Resurface
  • Ultrasonic Cleaning
Recommendations / Warranty:
  • Assembly and professional installation recommended.
  • Workmanship/parts warranty will only be available for professionally installed cylinder heads.




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