Crafted IAG Performance 1150 Series High Compression Closed Deck EJ25 Short Block 2006-2014 WRX / 2004-2021 STI / 2004-2013 Forester XT / 2005-2009 Legacy GT

Description

Designed for high-octane fuels such as E85 and race gas, the IAG 1150 High Compression Short Block is engineered to dominate on the drag strip while remaining suitable for street use. Optimized for high-horsepower applications, this short block increases compression and strengthens the engine to handle the most demanding performance builds. Compared to the standard 1150 Short Block, the high compression version raises the compression ratio to 9.9:1 on D Heads and 9.5:1 on B, V, and W Heads, unlocking additional power and efficiency necessary for racing applications.

Built for strength and reliability, the IAG 1150 features Stage 4 closed deck case halves with pinned mains secured by ARP hardware, providing exceptional durability under extreme conditions. The proprietary IAG Fire-Lock™ Head Gasket System ensures a tight seal, while the 14mm ARP/IAG head studs, nuts, and washers reduce the risk of head lift under high boost. This short block also incorporates IAG Tri-Beam +2mm forged connecting rods and a billet crankshaft, engineered to support additional oiling demands and prevent main bearing distortion, making it capable of handling the largest turbochargers and most extreme loads.

Every component of the IAG 1150 High Compression Short Block is 100% new. The custom 99.75mm forged pistons feature .250″ walls and .927″ wrist pins with electroless nickel plating for added durability. Case halves are CNC-machined and deck plate bored for precise piston-to-wall clearance, while the billet crankshaft is paired with ACL or King race bearings. The pistons are designed to be lightweight yet strong, featuring gas ports that improve ring sealing under high boost conditions. Their flat-top design reduces negative volume, increasing compression for aggressive racing setups.

Includes:

• Case Halves -Converted to Closed Deck from brand new OEM Subaru case halves, bored and honed to 99.75mm.
• Pinned Mains -Machine case for 9.5mm pinned mains and lined honed.
• Fire-Lock -IAG Fire-Lock™ receiver groove machining, latest solution to prevent head gasket failure on high horsepower and high boost Subaru’s – *IAG Fire-Lock™ head gaskets required
• Head Studs -Machined for 14mm Head Studs
• Pistons -IAG-Spec JE FSR 99.75mm 2618 Forged Pistons, Electroless Nickel Plated Tops & Ring area, Ring Set, .250″ wall / .927″ diameter H13 Wrist Pins, Clips, (Perfect Skirt Coating and Offset Wrist Pins)
• Connecting Rods -IAG-Spec +2mm Tri-Beam Connecting Rods with ARP 625+ Rod Bolts.
• Rod / Main Bearings -ACL or King Race Bearings.
• Crank -IAG-Spec Billet Crank
• Case / Main Bolts -ARP Main Bolts.

Note:

• Requires IAG Fire-Lock .051″ Head Gaskets with IAG-Spec Alloy Ring Set* PN# IAG-ENG-1741

Compression Ratio:

• 9.9:1 on D Cylinder Heads (EJ255)
• 9.5:1 on B, V and W EJ257 Heads