IAG Performance 800 Series FA20 (12.5:1 Compression Ratio) Closed Deck Short Block 2013-2021 BRZ / 2013-2016 FRS / 2017-2021 GT86 Trending

The IAG 800 Short Block is built for modified FA20 Subaru BRZs and FT86s that need a stronger short block to handle higher cylinder pressures from larger turbochargers. It features a proprietary closed-deck system to reinforce the OEM FA20 cylinder walls, IAG Spec H-Beam forged connecting rods, and enhanced head gasket sealing with o-rings and 1/2″ head studs—perfect for fully bolted-on and upgraded turbo setups.

Starting with new FA20 engine case halves, each block is machined for improved oil flow and assembled with IAG Closed Deck Inserts, which maintain coolant passages while transforming the block into a solid deck. O-ring grooves and drilled/tapped holes for 1/2″ head studs reduce head gasket failure under high cylinder pressures. The block is bored and honed to 86.1mm using our Sunnen SV-30 hone for precise piston-to-wall clearance. Assembly includes a 2020 FA20 crankshaft, IAG Spec H-Beam rods with ARP2000 bolts, and King or ACL bearings. Case halves are sealed with OEM bolts and sealant, and IAG Spec 86.1mm forged pistons complete the build.

Internal oil passages are inspected and optimized to ensure proper flow, addressing OEM limitations for improved reliability under boost.

The IAG 800 uses JE FSR 86.1mm forged pistons made from 2618 T6 Alloy. Asymmetrical skirts reduce weight and friction while maintaining strength. Smooth dome and dish radii promote excellent flame travel. Pistons are secured with .905 x 2.250″ x .210″ carbon steel wrist pins and Tru Arc locks. This block features 12.5:1 standard compression pistons, ideal for low-boost or stock applications.