The IAG Stage 2.5 Short Block is designed to solve the majority of common problems which plague modified EJ20 engines, especially at higher horsepower levels. The IAG Stage 2.5 short block builds off our Stage 2 Tuff block's strengths by adding our proprietary closed deck system. This system strengthens and supports the cylinder walls to prevent cracks that can occur with increased cylinder pressures. (This is the most common issue when increasing horsepower.) The Stage 2.5 EJ20 Short Block also features 92.5mm JE Forged Pistons and IAG Spec H beam connecting rods, along with ACL or King Race bearings. These components also significantly strengthen the common failure points such as cracked ring lands and spun bearings. These blocks are intended to be used with 2.0l EJ20 cylinder heads.

The IAG Stage 2.5 Short Block starts with brand new Subaru 2.0L engine case halves. Our machinists machine the assembled case halves in our Haas VF-4SS CNC mill to accept the IAG Closed Deck inserts, transforming the block into a solid deck. Next, a deck pair of deck plates are attached and the short block is bored and honed to 92.5mm in our in-house Sunnen SV-30 computer-controlled cylinder hone. IAG's in-house honing process allows us to set custom piston to wall clearances to ensure quiet operation and reduced oil consumption. The modified case halves are then assembled using a new Subaru 2.0L WRX crankshaft with improved oil passages and IAG-Spec Tuff H-Beam connecting rods with ARP rod bolts. IAG Short blocks feature ACL or King Race rod and main bearings and are all balanced and blueprinted. Finally, the case halves are sealed with new OEM main/case bolts and sealant.

Our unique closed deck system significantly increases the strength of the OEM case halves. This process supports the cylinder walls at the top of the case to prevent flexing and possible cracking where the case bolt reliefs are cut into the back of the cylinder wall.
During the installation process, we machine the assembled case halves in our Haas VF-4SS CNC mill to accept the IAG Closed Deck inserts. Once the case has been machined we heat it in an oven while freezing the specially machined inserts with liquid nitrogen. The inserts are then pressed into place and then machined to a mirror finish.
The unique inserts feature small passages that allow needed coolant flow to the deck surface. This means that the closed deck system does not affect the block's cooling ability and will not cause overheating, even in daily drivers.

Each Stage 2.5 Short Block features IAG Spec JE FSR 92.5mm Forged Pistons. These 2618 T6 Alloy high-strength pistons have been specifically designed to support increased cylinder pressures which come with more boost. FSR forgings reduce mass and wear caused by friction without sacrificing strength. 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 .210" wall 9310 steel wrist pins with Tru Arc locks.