THE IAG 1150 HIGH COMPRESSION SHORT BLOCK

Built for high-octane fuels such as E85 and race gas, the IAG 1150 High Compression 2.5L Closed Deck Short Block is the ideal choice for high-horsepower drag racing scenarios. While suitable for street use, it’s built to dominate the track. Compared to our regular 1150 Short Block pistons with compression ratios of 8.5:1 (D Heads, EJ255) and 8.2:1 (B, V, and W Heads, EJ257), the IAG High Compression 1150 steps it up to 9.9:1 on D Heads and 9.5:1 on B, V, and W Heads, unlocking more power and efficiency needed for race applications.

BUILT FOR SPEED AND POWER

This high compression Subaru block includes additional features to further strengthen the OEM case halves including Stage 4 Closed Decking and pinned mains secured with ARP case hardware. Our record-setting "Fire-Lock" Head Gasket system and 14mm head studs are used to ensure a tight seal even in extreme conditions. In addition, this short block also features IAG Spec "Tri-Beam" +2mm forged connecting rods. An IAG Spec Billet Crankshaft is used to support additional oiling and prevent main bearing distortion. The upgraded block, billet crank, connecting rods, race bearings, and forged pistons are able to support additional engine load produced by the largest turbochargers and the most demanding uses including competition drag racing.

BUILT WITH 100% NEW COMPONENTS

Every IAG Short Block is built with 100% new components. The modified case halves are assembled using an IAG-Spec Billet crankshaft that is matched to ACL or King race main bearings. Custom IAG TRI-BEAM +2mm connecting rods with ARP 625+ rod bolts are utilized, along with ACL or King race rod bearings. The case halves are sealed with OEM sealant and ARP main bolts. The IAG-Spec 99.75mm Custom Forged Pistons with .250" wall / .927" diameter wrist pins as well as electroless nickel plated tops and ring area are chosen to finish the IAG 1150 High Compression Short Block.

IAG CLOSED DECK WITH FIRE-LOCK SYSTEM

The IAG 1150 High Compression Short Block starts with brand new Subaru 2.5L EJ25 engine case halves. The case halves are split and the main webs are CNC machined in our Haas VF-4SS CNC mill for 9.5mm pins to reduce distortion and movement of the case in extreme conditions. The case halves are then reassembled and IAG machines the case to accept the IAG CLOSED Deck Inserts that transform the block into a solid deck. The unique inserts feature small passages that allow needed coolant flow to the deck surface. The case halves are then CNC machined for our new Fire-Lock™ head gasket solution that is loosely derived from diesel technology where a counterbore step is machined around each cylinder bore allowing specially sized fire rings to drop into the machined area and head gasket bores. The IAG 1150 case is CNC drilled and tapped to fit 14mm head studs. Utilizing the new Fire-Lock™ gasket solution, along with larger IAG / ARP 14mm head studs, nuts, and washers reduce the chances of the heads lifting under extreme boost conditions. The short block is then Deck Plate bored and honed to 99.75mm in our in-house Sunnen SV-30 cylinder hone. IAG's in-house honing process is able to set custom piston to wall clearances to ensure performance and reliability.

STRONG & LIGHT DESIGN

The IAG 1150 High Compression Short Block uses our IAG-Spec 99.75mm Custom Forged Pistons with .250" wall / .927" diameter wrist pins feature electroless nickel plated tops and ring area. IAG's custom pistons feature a lightweight design while increasing strength where you need it and are designed to work exclusively with the IAG +2mm Tri-Beam connecting rods. The wrist pin is short and is made from strong H13 tool steel. The pin piers are profiled to increase pin boss strength. Finally, IAG's pistons feature added gas ports that aid ring sealing in high boost conditions.

IAG HIGH COMPRESSION PISTONS

The IAG 1150 High Compression Short Block includes all the premium components of our 1150 short block, upgraded with custom high compression pistons. These pistons increase the compression ratio by reducing the pistons negative cc volume, and changing from a “dish” to a “flat top” style piston, making them ideal for racing applications where power and efficiency matter most. To ensure optimal performance, this short block requires consistent use of high-octane fuels like E85 or race gas. Pump gas is suitable only during the break-in process.