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IAG Stage 5 CNC Ported Heads Pkg Stage 5 CNC Ported Heads w/ +1mm Ferrea Valves & GSC S3 Cams N25 Casting

Engine Cylinder Head and Camshaft Kit


IAG Stage 5 CNC Ported Heads w/ +1mm Ferrea Valves & GSC S3 Cams for 18-20 STI N25 Casting.

  • New Head Castings, Fully CNC Ported with +1mm Ferrea Valves, Ferrea Drag Springs, GSC S3 Cams
Pricing: $7,479.99

Free ground shipping on all order over $100.00 (some exclusions may apply)


Subaru: WRX STI 18 - 21 Kanrai Edition / Sport-tech / Sport / STI / Type RA / Limited / Base / S209

  • Recommendations / Warranty: Assembly and professional installation recommended. Workmanship/parts warranty will only be available for professionally installed cylinder heads.
  • Stage 5 Ported Head Package Includes: (x2) Brand New Subaru OEM N25 Cylinder Head Castings, (x8) Ferrea 37mm (+1mm) Comp Plus Intake Valves, (x8) Ferrea 33mm (+1mm) Comp Plus Exhaust Valves, (x16) Ferrea Dual Valve Springs & Titanium Retainers, (x16) GSC Copper / Bronze Valve Guides, (x8) Ferrea 6mm Intake Valve Stem Seals, (x8) Ferrea 6mm Exhaust Valve Stem Seals, (x1) GSC S3 Billet Camshaft Set, (x16) OEM valve lifters, IAG Performance CNC Porting, Multi-Angle Valve Job, Drilling for compatibility with 1/2" or 14mm Head Studs, Cam Clearancing, Ultrasonic Cleaning

IAG's Stage 5 Cylinder Head Package utilizes a CNC porting program for the N25 heads that was developed over the past five years and tested on the most successful high-horsepower Subaru's. The ported head package starts with brand new N25 OEM WRX STI head castings directly from Subaru of America. The bare castings are visually inspected 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. CNC porting is not only an efficient way of machining the heads and offers consistent port results every time. 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. Short 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 Ferrea Copper Bronze valve guides that are shaped to improve airflow. Once all the new guides are in place they 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 Ferrea +1mm valves. At this point, the heads decks are resurfaced using our TS-3000 BlockMate that cuts the aluminum to a smooth even finish. After resurfacing, the heads are ultrasonically cleaned to remove debris and oils from the machining process. The heads are then reassembled using GSC Billet S3 camshafts designed for drag racing applications intending to make 750-1000 wheel horsepower. During final assembly, the cams are matched to Ferrea Dual Valve Springs and Titanium Retainers along with Ferrea valve stem seals then bench-lashed to a tolerance that is close to final specifications.


  • IAG-ENG-3055NS3
  • IAG-ENG-3055NS3
  • 887753779090
  • IAG Performance
  • New


Shipping Information

  • Item Requires Shipping
  • 92.0 lbs.
  • W16.0000” x H12.0000” x L20.0000”
  • Free ground shipping on all order over $100.00 (some exclusions may apply)

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