EJ25 Closed Deck Short Block

The IAG 750 EJ25 Subaru Closed Deck Short Block is engineered to resolve prevalent problems in modified EJ25 engines, especially those operating at higher horsepower outputs. Building upon the foundation of the IAG 550 block, this performance short block incorporates IAG’s proprietary closed deck system. This enhancement significantly strengthens and supports the cylinder walls, mitigating the risk of cracks that can arise from elevated cylinder pressures, a common failure mode in high-performance applications. Constructed entirely from new components, this short block begins with brand-new Subaru 2.5L engine case halves. These are precisely machined in-house to integrate IAG's Closed Deck inserts, effectively transforming the block into a solid deck design. The process includes the installation of deck plates, followed by boring and honing the block to 99.75mm using IAG’s specialized in-house process. This allows for custom piston-to-wall clearances, contributing to quieter operation and reduced oil consumption. The assembly is completed with a new 2017+ Subaru 2.5L nitride-treated STI crankshaft and IAG-Spec Tuff H-Beam connecting rods, equipped with ARP rod bolts. It utilizes ACL or King Race rod and main bearings, and the entire assembly is balanced and blueprinted. The short block is then sealed with new OEM main/case bolts and sealant, ensuring a robust and ready-to-install foundation for demanding builds. Key internal components include IAG-Spec JE FSR 99.75mm forged pistons, crafted from 2618 T6 Alloy for high-strength performance under increased boost pressures. These pistons feature an asymmetrical skirt design to reduce mass and friction wear. They are secured by .905 x 2.250" x .210" wall 9310 steel wrist pins, offering enhanced power support over standard pins. Optional “Hybrid” pistons are available for those utilizing EJ20 cylinder heads, eliminating the need for chamber matching. This engine has a power output rating of 750 BHP and is compatible with 2002-2014 Subaru WRX, 2004-2021 STI, 2005-2009 Legacy GT, and 2004-2013 Forester XT models.