The IAG 750 Short Block is designed to solve the majority of common problems which plague modified EJ25 engines, especially at higher horsepower levels. The IAG 750 short block builds off our IAG 550 block’s strengths by adding our proprietary closed deck system. This system strengthens and supports the cylinder walls to prevent cracks which can occur with increased cylinder pressures. (This is the most common issue when increasing horsepower.) The IAG 750 also features 99.75mm JE Forged Pistons and IAG Spec H beam connecting rods, along with ACL or King Race bearings. These components also significantly strengthen the common failure points such as cracked ring lands and spun bearings.

The IAG 750 Short Block starts with brand new Subaru 2.5L engine case halves. Our machinists machine the assembled case halves in our Haas VF-4SS CNC mill to accept the IAG Closed Deck inserts, transforming the block into a solid deck. Next, a deck pair of deck plates are attached and the short block is bored and honed to 99.75mm in our in-house Sunnen SV-30 computer controlled cylinder hone. IAG’s in-house honing process allows us to set custom piston to wall clearances to ensure quiet operation and reduced oil consumption. The modified case halves are then assembled using a new 2017+ Subaru 2.5L nitride treated STI crankshaft and IAG-Spec Tuff H-Beam connecting rods with ARP rod bolts. IAG Short blocks feature ACL or King Race rod and main bearings and are all balanced and blueprinted. Finally, the case halves are sealed with new OEM main/case bolts and sealant.

Our unique closed deck system significantly increases the strength of the OEM case halves. This process supports the cylinder walls at the top of the case in order to prevent flexing and possible cracking where the case bolt reliefs are cut into the back of the cylinder wall.
During the installation process we machine the assembled case halves in our Haas VF-4SS CNC mill to accept the IAG Closed Deck inserts. Once the case has been machined we heat it in an oven while freezing the specially machined inserts with liquid nitrogen. The inserts are then pressed into place and then machined to a mirror finish.
The unique inserts feature small passages that allow needed coolant flow to the deck surface. This means that the closed deck system does not affect the block’s cooling ability and will not cause overheating, even in daily drivers.

Each IAG 750 Short Block features IAG Spec JE FSR 99.75mm Forged Pistons. These 2618 T6 Alloy high-strength pistons have been specifically designed to support increased cylinder pressures which come with more boost. FSR forgings reduce mass and wear caused by friction without sacrificing strength. This is accomplished by using an asymmetrical skirt design instead of the traditional full-round skirt, also this reduces weight significantly. Featuring smooth flowing radii on the domes and dishes, the design promotes excellent flame travel. The pistons are secured to the rods with .905 x 2.250″ x .210″ wall 9310 steel wrist pins with Tru Arc locks. The thicker steel wrist pins support additional power over the standard .180″ pins.

The IAG 750 CNC Pocket Ported Competition Cylinder Heads are designed with the weekend racer in mind. These CNC pocket ported heads provide a significant upgrade in flow over the IAG 550 heads. These heads work great for cars with some race track duty (road, rally, auto-x, drag) and are designed to support up to 750 BHP with supporting mods. These heads include upgraded GSC Standard Size Valves, GSC Viton Valve Stem Seals, IAG Stage 1 Valve Springs with Titanium Retainers, and OEM Keepers. GSC S1 Camshafts are available with OEM valve lifter buckets. We also offer an optional chamber modification service (see below) for EJ20 heads to allow use on EJ25 short blocks.

Each IAG 750 Cylinder Head Set starts with new OEM castings from Subaru of America. The first step is to select your Year and Model of vehicle so that we may provide you with the right castings to fit your project. Next, you’ll select whether or not you want to include our optional GSC camshaft package. If selected, these heads will include new GSC S1 Camshafts and OEM Lifter Buckets for valve adjustment.

The bare castings are visually inspected and then fixtured into our in-house Centroid 5-axis CNC Machine. The Centroid CNC ports the intake and exhaust runners under the valves and blends them to the valve seat. Once the Centroid completes the port process, the heads undergo a cam clearance machining process which removes material from the lifter area where larger lift and duration cam profiles are known to contact the castings. The heads are then fixtured in our Newen Valve Guide and Seat Machine to cut all intake and exhaust seats with a multi-angle valve job that suits the flow characteristics of GSC’s standard size valves. At this point, the heads’ decks are resurfaced using our TS-3000 BlockMate, which 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 IAG Stage 1 Single Valve Springs and Titanium Retainers along with GSC Viton stem seals.

Pocket porting is enlarging and blending the area under the valve seat. This is one of the most critical areas to get right in any porting job. Luckily, our Centroid 5 axis cylinder head porting machine gets it perfect every time. The area about 1″ under the valve is enlarged and blended to ensure a smooth transition and increase power. The rest of the port is left alone because additional volume is not required at these power levels, and can even hurt velocity if there’s not enough airflow.

We selected these GSC Power-Division billet S1 camshafts for your IAG 750 Head Package. These will not drop any low end power, and will create more power and torque across the entire RPM range. These are perfect for stock frame upgraded turbos or up to higher horsepower upgrades. Along with the camshafts we’ll include all new OEM valve lifter buckets and set final lash.