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IAG Stage 5 Cylinder Head Package N Castings
Subaru STI 2018-2021
Features & Product Details
RallySport Direct now carries highly sought-after high-performance upgrades and accessories brought to you by IAG Performance.
These are the IAG Performance Stage 5 Cylinder Heads. These heads have been engineered with precision utilizing the best combination of components to sustain high horsepower and high boost builds. These heads start out as brand new OEM head castings directly from Subaru Of America, where the bare castings are inspected before fixtured onto IAG's in-house Centroid 5-axis CNC machine. This machine is considered to be one of the most advanced precision engine machining tools available in the world.
The Centroid CNC ports the intake and hard to reach exhaust "dog-leg" port runner to achieve consistent port results that are very difficult to achieve by hand. Once the Centroid completes the porting process the heads are then cleared for the cams, and it removes any material from the lifter area where large duration cam profiles are known to contact the castings. Shortly after, the heads are removed and drilled to fit larger 1/2" or 14mm head studs which are commonly used in high-horsepower builds. Then the OEM guides are pressed out in favor of GSC Manganese-Bronze valve guides that are shaped to improve the airflow. The heads are then reassembled using Ferrea Dual Valve Springs and Titanium Retainers along with Ferrea Intake and Exhaust Valve Stem Seals.