The IAG 550 Short Block is designed for modified EJ25 Subarus that need a stronger short block to support increased cylinder pressures created by additional boost pressure. The IAG 550 short block features IAG Spec H-Beam forged connecting rods. The upgraded connecting rods and race bearings are able to support additional engine load produced by larger turbochargers or increased boost which the OEM STI rods found in the Stock short blocks cannot support reliably.

Each IAG 550 Short Block starts with brand new EJ25 Subaru 2.5L, 99.5mm stock bore engine case halves as standard. The case haves are carefullly measured and assembled using a new 2017+ Subaru 2.5L nitride treated STI crankshaft, which is matched to ACL or King race main bearings. The IAG 550 Short Block features IAG Spec H-Beam Connecting Rods with ARP2000 rod bolts, along with ACL or King race rod bearings. The case halves are sealed with new OEM main case bolts and sealant. Finally, IAG Spec JE 99.5mm Forged Pistons are carefully selected, measured, and installed to finish off the short block.

Each IAG 550 Short Block features IAG Spec JE 99.5mm Forged Pistons. These 2618 T6 Alloy high-strength pistons have been specifically designed to support increased cylinder pressures which come with more boost. This is accomplished by using an asymmetrical skirt design instead of the traditional full-round skirt, also this reduces weight significantly. Featuring smooth flowing radii on the domes and dishes, the design promotes excellent flame travel. The pistons are secured to the rods with .905 x 2.250″ x .180″ wall carbon steel wrist pins with Tru Arc locks.