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2 in stock


IAG / Crest CNC Stage X Billet Aluminum EJ25 Subaru Short Block

The CNC Billet Aluminum 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.

Each IAG / Crest CNC Case is machined from 6061-T6 Aerospace Aluminum and features Darton Ductile Iron Sleeves. The block is designed with increased material thickness over the OEM cast aluminum case halves and adds a unique 4-bolt bottom end for additional strength.

The IAG / Crest CNC Stage “X” Block, (Formally Willall) is a complete short block built on the Crest billet platform, which also includes pistons, rods, bearings, crank, bore/hone, case bolts, 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 the stock case
  • Precision machined for a superior surface finish
  • Hard anodized to avoid marking or straining

IAG Stage X Complete Shortblock Includes:

  • Case –Crest Billet / Sleeved Case Halves
  • Fire-Lock™ –IAG Fire-Lock™ receiver groove machining, latest solution to prevent head gasket failure on high horsepower and high boost Subaru’s – *IAG Fire-Lock™ head gaskets required
  • 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.
  • Pistons –IAG-Spec JE FSR 99.75mm 2618 Forged Pistons, Electro-nickel Plated Tops & Ring area, Ring Set, .250″ / .927″ H13 Wrist Pins, Clips, (Perfect Skirt Coating and Offset Wrist Pins)
  • Connecting Rods –IAG-Spec +2mm Tri-Beam w/ ARP625+ Rod Bolts
  • Rod/Main Bearings –ACL/King Race Bearings
  • Crankshaft –IAG-Spec Billet Crank
  • Case / Main Bolts –ARP Main 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.

Power: The IAG / Crest CNC Stage X Short Block has a power output rating of 1100+BHP.

Head Gasket Required:

After years of research and development testing, the IAG Performance Fire-Lock™ head gasket is the newest solution to preventing head gasket failure on high horsepower and high boost Subaru EJ25 engines. This solution is loosely derived from diesel technology where a counterbore step is machined around each cylinder bore allowing specially sized fire rings to drop into the machined area and head gasket bores. The shims are designed to create a compression seal once the heads are installed and torqued into place. IAG fire rings are manufactured to a very strict tolerance from a proprietary alloy and are then put through a heat treatment process. The gaskets are manufactured from an asbestos-free composite raw material and feature a silicone based beading applied to critical areas to improve sealing around all water and oil passages. The combination of the alloy compression shims and gaskets assure maximum sealing for a Subaru EJ25 turbocharged engine.
*The IAG Fire-Lock™ gaskets require machine work for installation and are recommended for use with 14mm head stud hardware.

*The gaskets are sold in pairs with four Fire-Lock™ rings.

  • Composite Material
  • IAG-Spec Alloy Ring
  • Specifically designed for 14mm Head Studs
  • Silicone Beading
  • 100mm Bore
  • .051″ Thickness
  • Intended for High Horsepower, High Boost applications
  • IAG ARP 14mm Head Studs Required
  • Gaskets sold in pairs
    Install Notes:

1. If a block or cylinder head was previously o-ringed the groove must be filled and resurfaced before using this type of gasket.
2. These gaskets require IAG ARP 14mm head studs to achieve the required torque necessary for proper installation.
3. Due to the required torque, any block that was previously honed will need to go to the next size overbore.
4. Future servicing will require cylinder head resurfacing due to an imprint left from the Fire-Lock™ rings.

  • *IAG Fire-Lock™ .051″ Head Gaskets with IAG-Spec Alloy Ring Set* PN# IAG-ENG-1740 – Add to your order for an extra $299.99

14mm Head Studs Required:

  • IAG / ARP 14mm Head Stud Set Part# IAG-ENG-1711 – Add to your order for an extra $579.99


Hardware / Seal Option:

Not planning on reusing your original short block service plugs and covers? IAG offers a simple comprehensive cover and seal kit that includes (1) Rear main seal, (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. *Never reuse a rear main seal on a new short block. – Add to your order for an extra $125.99


Availability: Usually Ships in 6+ Months