IAG

IAG Stage 3 Extreme EJ25 Subaru Closed Deck Short Block WRX, STI, LEGACY GT, FORESTER (IAG-ENG-1354)

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  • Regular price $ 4,999.99


IAG Stage 3 Extreme Subaru EJ25 Closed Deck Short Block

The IAG Stage 3 Extreme 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. The case halves are then CNC machined with o-ring receiver grooves around the bore surface as well as drilled and tapped to accept larger 1/2" head studs that aids in preventing cylinder heads from lifting in high boost applications. Next, the short block is Deck Plate bored and honed to 99.75mm in our in-house Sunnen SV-30 the most advanced automotive cylinder hone available. 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 2017+ Subaru 2.5L nitride treated STI crankshaft that is matched to ACL or King race main bearings. Manley Turbo Tuff Tri-Beam connecting rods and ARP rod bolts are utilized along with ACL or King race rod bearings. The case halves are sealed with new OEM main/case bolts and sealant (upgrade to ARP mains and line hone service a la carte). IAG-Spec JE FSR 99.75mm Forged Pistons are chosen to finish the Stage 3 Extreme short block. 

Stage 3 Extreme Closed Deck Includes:
  • Case Halves - Converted to Closed Deck using brand new Subaru OEM case halves, bored and honed to 99.75mm.
  • O-Ringing - Machine and O-Ringed Deck Surface
  • Head Studs - Machine case to fit 1/2" head studs - *Head studs sold separately
  • Pistons - IAG-Spec JE FSR 99.75mm 2618 Forged Pistons, Ring Set, .180" Chromoly wrist pins, Clips, (Perfect Skirt Coating and Offset Wrist Pins)
  • Connecting Rods - Manley Turbo Tuff Tri-Beam / ARP2000 Rod Bolts.
  • Rod / Main Bearings - ACL or King Race bearings.
  • Crankshaft - Standard New Subaru Nitride Treated 2017+ STI Crankshaft.
  • Case / Main Bolts – Standard FHI Subaru case bolts.


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



Power: The IAG Stage 3 Extreme Short Block has a power output rating of 800BHP.


*All IAG short blocks are balanced and blueprinted.

These blocks are built to order and have a lead time of 2-4 weeks.  Free shipping includes the 48 continental states only and will be shipped in a reinforced triple wall cardboard box.   We are an authorized IAG dealer and an OEM Subaru parts dealership.