RalliSpec EJ25 Short Block S4 (1150bhp) - Race Spec Pro

RELY ON RALLISPEC'S 25 YEARS OF SUBARU ENGINE BUILDING EXPERIENCE

For those of you ready to really turn up the heat, we offer our Race Spec series of closed deck short blocks.  These short blocks feature 14mm head stud machining and are optionally machined to accept Fire Lock head gaskets for serious combustion pressure sealing capabilities.  

The Race Spec Pro utilizes our new IRP pistons, the optimal 2618 piston to provide both incredible power capability and high wear resistance.  IRP piston forgings utilize the highest quality advanced 2618/A1 alloy which are fully machined on advanced CNC machining centers under tight environmental controls.  Grain structure, piston dimensions, and shape are all precisely controlled so that piston expansion can be carefully regulated.   The crown and ring land areas are hard anodized to provide an exceptionally wear resistant surface while also controlling heat transfer.  A double bridged forging design and slipper skirt ensures incredible rigidity while keeping mass to a minimum making it superior for performance and reliability under extreme conditions.  At the same time these features add up to a piston that can be run very tight in the bore for low noise and optimal ring seal while keeping wear rates low for near-OEM type longevity in a street driven application.  No other piston comes even close.  Note that our Race Spec series is built with a bit larger piston clearance than our Street Spec Pro in order to accommodate more extreme operating conditions.

The Race Spec series feature a closed deck block for increased cylinder strength under the extreme combustion pressures required to generate big power levels.  The Race Spec Pro takes block rigidity to the next level by dowel pinning the main bearing webs and fitting ARP main bolts torqued to a considerably higher level than stock.  This process helps to maintain the main bearing bore geometry under extreme forces and reduces the possibility of bearing failure.  Line honing the main bearing bores is required with this process and allows for more precise and accurate bearing clearances.  This block uses a 300M tri-beam forged connecting rod with ARP Custom Age 625+ bolts to handle the biggest power levels.  300M is an aerospace alloy that provides approximately 10% higher strength than 4340 chromoly while also improving on toughness and fatigue strength. 

Every short block is assembled by our master engine technician with 25 years of Subaru performance engine building experience in our dedicated engine room to exacting specifications.  All relevant engine specifications are logged and a detailed blueprint sheet is provided.

Built to order w/ typically a 2 week lead time.

Covered by a 1 year limited warranty.

SHORT BLOCK SPECS

• • Block Case - Closed Deck EJ257 w/ Optional Fire Lock Grooves
  • Block Reinforcement - Pinned Mains w/ ARP Main Bolts
    
  • Crankshaft - Salt-bath Nitride Hardened 79mm Stroke
    
  • Head Stud Thread - 14 x 2.00mm
    
  • Pistons - RalliSpec IRP 2618 Forged 8.2CR (8.6CR w/ D25 Heads)
  • Pin Wall Thickness - 0.250in
  • Connecting Rods - RalliSpec 300M Tri-Beam PRO Series by Saenz
  • Rod Bolts - ARP Custom Age 625+
  • Bearings - Calico Coated ACL Tri-metal Rod and Main
  • Static Balance Tolerance - 1/3 gram

Fits the following:

• STI EJ257
• WRX EJ255
• EJ207/EJ205 w/ Cylinder Head Chamber Matching