IAG Performance

IAG-ENG-1600

IAG / Willall Billet Aluminum EJ25 Subaru Case Halves For WRX, STI, Forester XT & Legacy GT


Using the same world-leading technology found in Willall’s incredible billet GT-R block, the billet EJ case seeks to change the Subaru performance tuning market by reinventing the EJ and addressing virtually every weakness that exists in max-power builds.

Case Features:

  • Machined from solid billet 6061-T6 Aerospace grade aluminum
  • Darton Ductile iron sleeves
  • Increased material thickness in all known weak points (around head studs, bottom end location)
  • Unique 4 bolt bottom end strengthening
  • Threads are rolled into the block rather than conventionally cut for much greater strength
  • Full cooling system operation
  • Radiused coolant and oil galleries for improved flow and less foaming/turbulence
  • Fits all factory engine bay ancillaries (i.e. AC/PS/etc.)
  • Multiple Times stiffer and stronger than stock case
  • Precision machined for superior surface finish
  • Hard anodized to avoid marking or straining

Additional Options:

  • Bore & Hone: Bore & Hone to customer specification $300
  • O-Ring: O-Ring Deck $200
  • Case Bolts: ARP Case Bolts $450
  • Head Studs: IAG / ARP 14mm Head Studs, nuts, and washers - $550. *14mm head studs are required for this block

Minimum Requirements To Build & Assemble:

  • ARP Case Bolts (Sold separately)
  • 14mm Head Studs (Sold separately)
  • Internal components (Pistons, Rods, Bearings, Crank, All sold separately).


*Attention: Special note about using ARP Case Bolts - IAG installs ARP CASE BOLTS with 30W engine oil using OEM SUBARU torque specs and procedures. Other torque specs and lubricants may lead to case distortion damage.

Vehicle Compatibility:
2002-2005 Subaru WRX requires mods
2006-2014 Subaru WRX
2004-2020 Subaru STI 
2005-2009 Subaru Legacy GT
2004-2013 Subaru Forester XT

*Pictures used for marketing purposes only, actual products may vary

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