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.