950 EJ25 2.5L Subaru Closed Deck Short Block

The IAG 950 EJ25 is a high-performance 2.5L Subaru closed deck short block engineered for "weekend racers" and built to support up to 950 BHP. It utilizes brand new Subaru 2.5L engine case halves, which are then converted to a closed deck configuration in-house using a Haas VF-4SS CNC mill and IAG's proprietary inserts. This process significantly strengthens the block, preventing flexing and cracking. The block is precision bored and honed to 99.75mm, with custom piston-to-wall clearances set for quiet operation and reduced oil consumption. The "Fire-Lock™" head gasket system is a key feature, separating combustion chamber sealing from fluid sealing to prevent head gasket failures, even under high boost and horsepower. This system requires machining a lip at the top of each cylinder to accept the Fire-Lock™ ring, with separate gasket bodies sealing oil and coolant passages. The block is machined to accept 14mm head studs, which are sold separately. Key internal components include IAG-Spec JE FSR 2618 forged pistons with electroless nickel plating, H13 tool steel wrist pins, and JE's Perfect Skirt coating. Connecting rods are IAG-Spec Tuff H-Beam +2mm with ARP 625+ rod bolts. It is assembled with ACL or King Race rod and main bearings and a new Subaru nitride treated 2017+ STI crankshaft. The compression ratio is 9.1:1 with D Cylinder Heads (EJ255) or 8.8:1 with B, V, and W EJ257 Heads using IAG Fire-Lock™ head gaskets. Head studs and IAG Fire-Lock™ head gaskets are required and sold separately.