IAG 1150 2.35L Destroked Long Block Engine w/ IAG 1150 Heads for 02-14 WRX, 04-21 STI, 04-13 FXT, 05-09 LGT

IAG’s 1150 EJ25 2.35L Destroked Closed Deck Short Block is built for power, capable of handling up to 1150 BHP. While still a streetable block, the 1150 is optimized for the track. This hand assembled block is based off of our 1150 short block and features an IAG Spec billet 75mm crankshaft, custom IAG Spec +2mm Tri-beam forged connecting rods and ARP 625+ rod bolts. Also included in the assembly are JE 99.75mm FSR 2618 custom pistons that have been treated with electroless nickel-plating, creating a hard-wearing surface that offers detonation resistance and heat reflection. This strengthened short block, combined with a billet crank, race bearings, along with forged connecting rods and pistons delivers a rock-solid foundation that is able to endure intense engine loads generated by large turbochargers and high-powered racing conditions, including competition drag racing.

Featuring a shorter stroke, these +2 rod engines reduce piston speeds, optimizing the rod-to-stroke ratio and increasing piston dwell time at top dead center. This results in improved combustion efficiency and reduced stress on engine components at high RPMs. In terms of performance, this means increased power output, extended ring life, and the ability to rev higher—making this short block an ideal choice for track days, racing, or competition drag racing applications. Our recommended maximum rev limit is 9,000 RPM for these short blocks.

The 1150 EJ25 Short Block starts with brand new Subaru 2.5L engine case halves. Our expert 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 Haas mill also cuts a groove at the top of each cylinder to accept the Fire-Lock™ head gasket rings and drills each head bolt hole for 14mm head studs. The modified case halves are then assembled using a new IAG Spec billet 75mm crankshaft, custom IAG Spec +2mm Tri-beam forged connecting rods and ARP 625+ rod bolts, along with JE 99.75mm FSR 2618 custom pistons. IAG Short blocks feature ACL rod and main bearings and are all balanced and blueprinted. Finally, the case halves are sealed with new ARP main/case bolts and sealant.

The IAG 1150 EJ25 2.35L Destroked Closed Deck Short Block features our proprietary "Fire-Lock™" Head gasket system. This system has been proven in our record setting race cars to be the strongest Subaru head gasket system ever produced. To achieve these results, our engineers separated the combustion chamber sealing from the fluid sealing aspects of the head gaskets. Our machinists carefully machine a lip at the top of each cylinder to accept the "Fire-Lock™" ring. With the ring locked in place, it stands proud above the deck, providing a superior seal. The separate gasket bodies take care of sealing oil and coolant passages and keeping them out of the combustion chamber. 14mm Head studs hold the assembly together.

Our innovative 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 1150 Short Block also features our exclusive case bolt reinforcement plugs, which are threaded and indexed to the deck surface for additional case strength. Our distinctive 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.

The IAG 1150 Short Block features JE 99.75mm FSR 2618 custom pistons, engineered to deliver outstanding performance for both street driving, as well as for drag, road and rally racing applications. These pistons feature thicker ringlands and are treated with electroless nickel-plating, resulting in a stronger piston that can stand up to highly boosted applications. Additionally, they come equipped with .240" H13 tool steel wrist pins, providing a significant upgrade over standard chromoly pins, ensuring enhanced reliability under extreme conditions.

A common failure point of the OEM Subaru short block are the piston ringlands. The metal ledges on the pistons that hold the compression rings in place can withstand regular usage but are prone to failure when used with modified components. Cracked or broken ringlands often lead to increased oil consumption and eventual bearing failure if the oil is not closely monitored. In contrast, the increased ringland thickness on the custom JE pistons used in the IAG 1150 Short Block are designed to match up to 1150’s capabilities, ensuring durability and reliability even under high-performance conditions.

The OEM EJ25 pistons continue to be produced using a hypereutectic cast design. This casting method is susceptible to irregularities in both the casting process and the materials used, leading to potential weaknesses in the pistons. This is where our custom JE pistons come in; forged from a durable 2618 T6 Alloy with a unique silicone additive, these JE pistons effectively absorb the direct shock and impact of combustion. Engineered to withstand ringland damage due to detonation and preignition, they feature a higher strength material and have been custom designed to feature thicker ringlands.

The IAG 1150 CNC Ported Drag Cylinder Heads are designed for drag racing and competition. These fully CNC ported heads provide a significant upgrade in long term performance over the IAG 950 heads. These heads work great for cars where getting the most power with maximum reliability is the goal. The IAG 1150 heads are the best heads available for high-horsepower drag racing. They are designed to support up to 1150 BHP with supporting mods. These heads include upgraded Ferrea Comp Plus Valves, GSC Viton Valve Stem Seals, Upgraded GSC Valve Guides, Ferrea Dual Drag Valve Springs with Titanium Retainers, and Ferrea Keepers. GSC S2 or S3 Camshafts are available with Kelford DLC Coated valve lifter buckets.

This IAG 1150 fully CNC ported head package starts with brand new WRX STI 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. The Centroid CNC ports the intake and hard to reach exhaust "dog-leg" port runner. The benefit of CNC porting is not only an efficient way of machining the heads, it also offers consistent port results that are hard to achieve by hand. 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. Shortly 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 GSC Manganese-Bronze valve guides that are shaped to improve airflow. 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 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 Ferrea's +1mm 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 Ferrea Drag Springs and Retainers along with Ferrea Viton stem seals..

Cylinder head porting has been around since the invention of the internal combustion engine. It can be done by hand with a die grinder and some cartridge rolls, and a seasoned professional can likely get a good result that way. Unfortunately, doing porting this way requires a lot of experience and care. One slip of the die grinder can ruin your cylinder head. This is where CNC porting comes in. Using our Centroid 5 axis CNC porting machine we can achieve the same results every time we put a set of heads into the machine. Every cylinder head comes out exactly the same and uses our race-proven, computer controlled, CNC porting program to guarantee results.

To get the most out of these heads you'll want to select the GSC Power-Division billet S2 camshafts for your IAG 1150 Head Package. These cams are built to suit the higher horsepower these heads will support. With a power range of 500 WHP and up, you need some additional supporting mods to utilize the true potential of the S2s. Our IAG 1150 Short Block, an upgraded turbocharger and fuel system, and a quality engine management system are key.

If you're targeting maximum power over 1000 WHP and willing to give up some low end drivability, the GSC S3 cams are the way to go. PLEASE NOTE THAT THESE CAMS REQUIRE A STANDALONE ECU AND MAY NOT FUNCTION CORRECTLY WHEN AVCS IS USED. Along with the camshafts we'll include all new Kelford DLC Coated valve lifter buckets and set valve lash so the engine will be ready to install and run.