IAG Performance Stage 5 CNC Ported Heads w/CM w/+1mm Ferrea Valves S20 (Cams/Lifters Sold Sep)

IAG's Stage 5 Cylinder Head Package utilizes a CNC porting program for the B25 heads that was developed over the past five years and tested on the most successful high-horsepower Subarus. The ported head package starts with brand new B25 2004-06 STI, 2004-05 Forester XT and 2005-06 Legacy GT 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, 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 it also offers consistent port results every time. Next, the heads receive our combustion chamber modification in which the shape of the chambers are machined to match those of an STI head. Once the Centroid completes this process the heads undergo a cam clearance process to remove material from the lifter area where large duration cam profiles are known to contact the castings. The heads are then drilled to fit larger 1/2" or 14mm head studs for maximum clamping force. Next, the OEM guides are removed and replaced in favor of Ferrea Copper / Bronze valve guides that offer greater heat dissipation, lubricity properties and are shaped to improve flow. 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 Serdi 3.0 Valve Guide and Seat Machine to cut all intake and exhaust seats with multi-angle valve job that suits the flow characteristics of Ferrea Comp Plus +1mm valves. At this point, the heads decks are resurfaced using our TS-3000 BlockMate that 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 Dual Valve Springs and Titanium Retainers along with Ferrea intake and exhaust valve stem seals.