IAG Stage 2.5 EJ25 Closed Deck Shortblock

IAG Stage 2.5 EJ25 Closed Deck Shortblock: The IAG Stage 2.5 Short Block starts with brand new Subaru 2.5L engine case halves. IAG machines the case halves assembled together in our Haas VF-4SS CNC mill 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. Next the short block is Deck Plate bored and honed to 99.75mm in our in-house Sunnen SV-10. IAG‘s in house honing process is able to set custom piston to wall clearances to best fit your needs. The modified case halves are then assembled using a new 2012+ Subaru 2.5L heat-treated STI crankshaft that is matched to ACL Race main bearings. Manley H Tuff connecting rods and ARP rod bolts are utilized along with ACL Race rod bearings. The case halves are sealed with new OEM main/case bolts and sealant (upgrading to ARP mains requires line honing). Manley Spec 99.75mm Platinum Forged Pistons are chosen to finish the Stage 2.5 short block.

Stage 2.5 Closed Deck Includes:

  • Case Halves - Converted to Closed Deck using brand new Subaru OEM case halves, bored and honed to 99.75mm.
  • Pistons - Manley 99.75mm Platimum Forged Pistons
  • Connecting Rods - Manley H Tuff / ARP Rod Bolts.
  • Rod / Main Bearings - ACL Race.
  • Crankshaft - Standard New Subaru Heat-Treated 2012+ STI Crankshaft.
  • Case / Main Bolts – Standard FHI Subaru case bolts.


Additional Options Available:

  • Oil Pump - ACL Orbit High Volume Oil Pump - $249 or 11mm Subaru Oil Pump - $185.95
  • Head Gaskets - JE Pro Seal .039 inch Head Gaskets - $96 or Cosworth 1.1mm - $222
  • Hardware / Seal Option - $99.99 (Wrist pin plugs, washers, separator cover, bolts, etc. In case you don’t want to transfer from the original engine).


Compression Ratio:

  • 8.5:1 on D Cylinder Heads (EJ255)
  • 8.2:1 on B, V and W EJ257 Heads with standard thickness gasket.


Head Gasket Recommendations:

  • *IAG Recommends JE Pro Seal .039 inch head gaskets for B and D casting cylinder heads.
  • *IAG Recommends Cosworth 1.1mm head gaskets for all V and W casting cylinder heads.



The IAG Stage 2.5 Short Block has power output rating of 700BHP.

*All IAG short blocks are balanced and blueprinted.



Hardware / Seal Option:

Subaru EJ25 Seal Kit
Not planning on reusing your original short block service plugs and covers? IAG offers a simple comprehensive cover and seal kit that includes the (3) OEM wrist pin plugs, (3) OEM wrist pin plug washers, (1) OEM separator cover, (6) OEM separator cover bolts, (1) OEM wrist pin service cover, (1) OEM wrist pin service cover O-ring and (2) OEM wrist pin service cover screws. *If you are reusing your original wrist pin service plugs and covers always replace the (3) OEM wrist pin plug washers and (1) wrist pin service cover O-ring before installing a short block to avoid potential leaks.

  • Item #: IAG-ENG-1250
  • Manufacturer: IAG Performance
  • Manufacturer's Product Number: IAG-ENG-1250

IAG Stage 2.5 EJ25 Closed Deck Shortblock

Price: $3,999.99
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