IAG 1150 2.35L Closed Deck Short Block - 1150 BHP, 2002-2014 WRX & 2004-2021 STi

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 (Not Included) 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