top of page

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. The Stage “X” Block is a complete short block built on the Willall billet platform, which also includes pistons, rods, bearings, crank, bore/hone, case bolts, o-rings, line hone, and final assembly and blueprinting. 

Stage X Billet EJ25 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

IAG Stage X Complete Shortblock Includes:

  • Case - WREJBB Billet / Sleeved Case Halves
  • Pistons – IAG-Spec 99.75mm 2618 Forged Pistons w/ Extreme .210” Wrist Pins
  • Connecting Rods – IAG-Spec +2mm Tri-Beam w/ ARP625+ Rod Bolts
  • Rod/Main Bearings – ACL/King Race Bearings
  • Crankshaft – Manley Billet Crank
  • Case Bolts – ARP Main Bolts
  • O-Ring – Deck surface o-ringed
  • Machining - Machined for 14mm Head Studs *(Studs sold separately / Note the proper head gaskets or head gasket modifications are required for proper fitment with 14mm studs.

Additional Options Available:

  • Head Studs - IAG / ARP Spec 14mm head studs, nuts, and washers - $550
  • Head Gaskets - IAG / JE Proseal .039in Head Gaskets with 14mm Head Stud Provisions - (1 Pair) $159.98, Cosworth Head Gaskets modified for 14mm Head Studs (1 Pair) - $225 *Note specific gaskets are required for this block.
  • Oil Pumps - ACL / Orbit Oil Pump - $229 / Cosworth 11mm Oil Pump - $599 / OEM Subaru 11mm Oil Pump - $194.95
  • Hardware / Seal Option - $99.99 (Includes: Wrist pin plugs, washers, separator cover, bolts, etc. In case you don’t want to transfer from the original engine).

Required :

  • 14mm Head Studs, Head Gaskets, Oil Pump all sold separately, and are required to run.

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 / Willall Stage X Short Block has power output rating of 1000+BHP.

*All IAG short blocks are balanced and blueprinted. 

IAG / Willall Stage X Billet Aluminum EJ25 Subaru Short Block

    Product Page: Stores Product Widget
    bottom of page