EJ25 - Track Mod, Closed Deck Short Block

CJM Track Mod - CLOSED DECK EJ25 

The Ultimate Subaru EJ25 Foundation for Track Days

Reinforced for Maximum Power and Reliability

Can-Jam Motorsports Closed Deck System transforms the OEM EJ25 block into an ultra-strong foundation built for high-boost, high-power applications.

Our proprietary billet aluminum inserts reinforce the cylinder tops in the areas most prone to movement and cracking — without compromising cooling performance.

Unlike traditional conversions, CJM’s integrated coolant passages allow continuous flow around each cylinder, ensuring your engine runs cooler than comparable closed deck blocks on the market.

Whether you’re building a 750bhp street setup or a full race motor, the CJM Closed Deck delivers the strength and temperature control you need to push limits confidently.

Precision Engineering — 100% In-House

Every CJM Closed Deck conversion is performed start-to-finish in our facility by our own engineers and machinists.

Start with OEM Quality: Brand-new EJ25 bare case halves form the foundation.

1. CNC Machining: Twelve custom pockets are precisely cut to accept our billet inserts.
2. Thermal Fit Process: The case is heated while inserts are cryogenically cooled, then press-fitted together for a perfect, interference-free bond.
3. Final Machining: After cooling, the deck is resurfaced with diamond tooling, coolant and bolt passages are re-cut, and the surface is finished perfectly flat.

This process produces a tight, dimensionally accurate closed deck that dramatically improves reliability under extreme boost and high cylinder pressures.

CJM GOLD-ANODIZED BILLET INSERTS

Purpose-built for both strength and efficiency, our proprietary billet inserts feature:

Material: CNC-machined billet aluminum for maximum rigidity.

• Finish: Gold anodized for corrosion resistance
• Cooling Advantage: Integrated water passages preserve coolant flow and improve thermal balance compared to conventional closed-deck blocks.
• Structural Strength: Billet design minimizes bore distortion, even under extreme cylinder pressure.
• Precision Fit: Each insert aligns perfectly and seals consistently for long-term reliability.
• Thermal Stability: Maintains bore roundness and proper clearances through repeated heat cycles.

The result: a robust, efficient, and cooler-running closed-deck block that outperforms standard conversions.

Bore & Hone Service
Following the closed-deck conversion, the case must be bored and honed to restore proper piston clearance — an essential final step for maximum performance and longevity.

The block is honed to 99.75mm and pistons are matched

Available Now for Engine Builders

For those who prefer to build their own engines, CJM offers Closed Deck EJ25 case halves for individual purchase.
Install your own crank, rods, and pistons — and enjoy the confidence that your build will handle serious power and boost.