IAG Stage 4 Cylinder Head Package N Castings - 2018-2021 Subaru STI

Please Note: This item is not eligible for standard ground shipping and must be delivered via freight. To receive a custom invoice that includes all applicable freight charges, kindly contact us by email or phone.

 

STOCK NOTICE: At times, this item carries a 6-8 week build time when not in stock. 

 

 

 

RallySport Direct now carries highly sought-after high-performance upgrades and accessories brought to you by IAG Performance.

 

These are the IAG Performance Stage 4 CNC Ported 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 also utilize a CNC porting program for the WRX STI heads that has been under development for the last 5 years, and they have been tested on the most successful high-horsepower Subarus. 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 GSC Beehive Valve Springs and Retainers along with the GSC Viton Stem Seals.

 

 

FEATURES:

• The heads start out as brand new castings from Subaru Of America
• Heads are then machined in-house at IAG utilizing a Centroid 5-axis CNC machine
• The Centroid CNC ports the intake and hard to reach "dog leg" exhaust ports
• The Centroid CNC provides consistent porting results
• The heads will then undergo a cam clearance machining process
• Material will be removed from the lifter area where larger duration cams are known to make contact with the castings
• The heads are then drilled to fit 14mm or 1/2" head studs which are commonly used in high-horsepower builds
• OEM guides are then pressed out in favor of GSC Manganese-Bronze valve guides that are shaped to improve airflow
• Once the guides are in place they are diamond-honed in IAG's honing station
• The heads are then fixtured to IAG's Serdi 3.0 Valve Guide and Seat Machine to cut all the intake and exhaust seats
• A multi-angle valve job is performed to suit the flow characteristics of the GSC +1mm valves
• Heads are then resurfaced using IAG's TS-3000 Blockmate that cuts the aluminum to a smooth and even surface
• The heads are then ultrasonically cleaned to remove debris and oil from the machining process
• Reassembly then begins using GSC Beehive Valve Springs and Viton Valve Stem Seals

 

 

CONTENTS INCLUDE:

• (2) Brand new Subaru OEM cylinder head castings
• (8) GSC 37mm (+1mm) Intake Valves
• (8) GSC 33mm (+1mm) SuperAlloy Exhaust Valves
• (16) GSC BeeHive Springs And Retainers
• (16) GSC Manganese-Bronze Valve Guides
• (16) GSC Valve Stem Seals
• IAG Performance CNC porting
• Multi-angle valve job
• Drilling for compatibility with 14mm or 1/2" head studs
• Machined cam lobe clearance
• Resurfacing
• Ultrasonic cleaning

 

 

NOTES:

• The cams and lifters are sold separately
• Professional installation required

 

 

IMPORTANT DELIVERY NOTE:

Your order is shipping Via Truck Freight which requires you to be available at the time of receipt. There is a possibility the trucking company will try to schedule a delivery time with you.

At the time of delivery, the driver will hand you the delivery receipt also referred to as the bill of lading, you will use this to notate any damages to the shipment. It is important that you fully inspect the shipment from all sides and notate any dents, punctures or rips in the outside packaging on the delivery receipt. Once you've inspected your shipment from the outside, you will need to open it and check the product in its entirety for damages and notate them if any.

If there is no damage sign for the package and enjoy!

In the rare case, you do find that your order arrived with damages, it is important you follow these steps.

- Do not refuse the product
- Document the damages in as much detail as possible on the Bill of Lading
- Take numerous photos from all angles (including packaging)
- Keep the product and contact the shipping company to start the damage claim
- Contact us either by phone or email for the next steps

In the situation where the delivery driver is unable to wait for you to open and inspect your product, simply document "driver was unable to wait for inspection." All damage must be noted on the Bill of Lading before signing and initiating a damage claim. If the damage is not notated before signing for the item it is assumed to be in good condition. This will forfeit the ability for a shipping claim and you will not be eligible for refund or replacement.