IAG Performance 1150 Destroked 2.35L Closed Deck EJ25 Short Block 2006-2014 WRX / 2004-2021 STI / 2004-2013 Forester XT / 2005-2009 Legacy GT Warranty Included

The IAG 1150 EJ25 2.35L Destroked Closed Deck Short Block is built for extreme power, supporting up to 1150 BHP while remaining streetable. Designed for high-performance and track use, this hand-assembled block features an IAG Spec billet 75mm crankshaft, custom +2mm Tri-beam forged connecting rods with ARP 625+ rod bolts, and JE 99.75mm FSR 2618 custom pistons treated with electroless nickel-plating for detonation resistance and heat reflection. Combined with race bearings, forged rods, and a billet crank, this short block provides a rock-solid foundation for large turbochargers and high-RPM racing applications.

The shorter stroke reduces piston speeds, optimizing the rod-to-stroke ratio and increasing piston dwell time at top dead center. This improves combustion efficiency, reduces stress on engine components, extends ring life, and allows for higher revs—recommended up to 9,000 RPM—making it ideal for track, road racing, and competition drag use.

The block starts with new Subaru 2.5L case halves, machined to accept IAG Closed Deck Inserts that reinforce the cylinder walls while maintaining coolant flow. O-ring receiver grooves and 14mm head bolt holes are machined to improve head gasket sealing. The assembly includes the billet crankshaft, Tri-beam rods, ARP bolts, JE FSR pistons, and ACL rod and main bearings. All blocks are blueprinted, balanced, and sealed with new ARP bolts and sealant.

The closed deck system supports cylinder walls at the top of the block, preventing flex and cracking. Inserts are pressed, machined to a mirror finish, and paired with case bolt reinforcement plugs for added durability. Coolant flow remains unaffected, ensuring safe operation for street or track use.

JE 2618 T6 Alloy 99.75mm FSR pistons feature thicker ringlands, electroless nickel plating, and .240″ H13 tool steel wrist pins for maximum strength and reliability under boost and high-RPM conditions.

IAG’s proprietary Fire-Lock™ system separates combustion chamber sealing from fluid sealing, with machined cylinder lips for the Fire-Lock™ rings. This design ensures superior head gasket sealing under extreme pressure, eliminating a common failure point in high-power EJ25 engines.

Includes:

• Case Halves –Brand new Subaru OEM case halves
• 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 –JE 99.75mm FSR 2618 Custom Pistons and .240″ H13 Tool Steel Wrist Pins with JE Pro Seal Ring Set
• Connecting Rods –Custom IAG Spec +2mm Tri-Beam Forged Connecting Rods with ARP 625+ Rod Bolts
• Rod / Main Bearings –ACL Race Bearings
• Crank –IAG Spec Billet 75mm Crankshaft
• Case / Main Bolts –ARP Case Bolts.