IAG Stage 2.5 Closed Deck Short Block

2004-2021 Subaru STI / 2006-2014 WRX

Ships for free in the 48 states

SKU: IAG-ENG-1252We price match!

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The Stage 2.5 EJ25 Closed Deck Short Block will support up to 700 BHP in the Subaru STI. 
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IAG Stage 2.5 Tuff EJ25 Closed Deck Short Block


  • Brand new Subaru OEM case halves converted to Closed Deck 
  • Unique inserts on the block feature small passages that allow needed coolant flow to the deck surface
  • Bored and honed to 99.75mm
  • IAG-Spec JE FSR 99.75mm 2618 forged pistons w/ skirt coating 
  • .180" Chromoly wrist pins
  • IAG Spec Tuff H-Beam connecting rods
  • ARP2000 Rod bolts
  • ACL Rod and Main Bearings
  • Standard new Subaru Nitride Treated 2017+ STI crankshaft
  • Standard FHI Subaru case bolts/main bolts
  • Supports up to 700 BHP



  • Compression ratio with D cylinder heads: 8.5:1
  • Compression ratio with B, V, and W EJ257 heads with standard thickness gasket: 8.2:1



The IAG Performance Stage 2.5 Hybrid Closed-Deck Short Block has been designed for power-hungry enthusiasts who want to increase the displacement and low-end torque of their Subaru that was originally equipped with the EJ20 2.0 engine.  The Hybrid 2.5 features pistons that are designed to lower the compression and math the EJ20 cylinder heads without the need to modify the cylinder head chamber. 

Each 2.5L Hybrid Shortblock will start with a brand new Subaru 2.5L engine case halves in which IAG machines them, and they are assembled together in-house and are CNC milled to accept the IAG closed-deck inserts that transform the block into a solid deck. The unique inserts feature small passages that allow needed coolant flow to the deck surface. The short block is then deck plate bored and honed to 99.75mm in IAG's in-house cylinder hone. The modified case halves are then assembled using a brand new 2017+ 2.5L nitride-treated STI crankshaft that is matched to ACL rod and main bearings. The rest of the blueprinted engine features IAG-Spec JE FSR 99.75mm 2618 forged pistons w/ skirt coating, and IAG Spec Tuff H-Beam connecting rods that are assembled with ARP 2000 rod bolts.

This is a great rebuild option for those of you who want an assembled short block built by one of the best industry-leading performance shops available and is rated to 700 BHP. 




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