EJ257 Closed Deck Conversion on a Budget | EPOXY54
EPOXY54 fills the open-deck water jacket with 21,000 PSI epoxy, stopping bore distortion in high-boost EJ257, EJ205, and FA20DIT builds. No machine shop required.
- Subaru EJ257, EJ205, and FA20DIT engines all use open-deck aluminum block construction.
- Under high boost, the open water jacket allows the cylinder bores to flex and distort.
- Bore distortion causes uneven ring seal, increased blow-by, and accelerated wear — a known issue on high-boost STI and WRX builds.
- The EJ257 in the STI and the FA20DIT in the WRX are especially vulnerable on aggressive power builds.
- Traditional fix: closed-deck machine job — costs $2,000+ and requires a full engine rebuild.
- Fills the open water jacket with structural epoxy rated at 21,000 PSI.
- Non-expanding and non-shrinking — zero risk to piston clearances.
- Thermal expansion matches cast aluminum 1:1, so it moves with the block through heat cycles.
- Coolant resistant — will not deteriorate with long-term coolant exposure.
- Partial fill retains OEM cooling and keeps the car fully daily driveable.
- No machining, no special tools. Includes video and written instructions.
Installation: 5 Steps
No machine shop. No special equipment. Do it in your own garage.
Fill the water jacket with a temporary solute like sugar or salt. This creates the void space for coolant passages.
Mix EPOXY54 and pour it to fill the top ¾" of the block. The runny consistency ensures a clean, seamless application.
Allow the epoxy to cure completely. Unlike other closed deck solutions, EPOXY54 is ready in just 24 hours without the need for machining.
Following your head gasket design, drill the necessary coolant passages through the cured epoxy.
Dissolve the temporary solute with water and flush it out, leaving behind a perfectly reinforced block with optimal cooling.
How EPOXY54 Compares
EPOXY54 vs. the alternatives — on every dimension that matters for a Subaru build.
| Feature | EPOXY54 | Block Guard (CSS) | Cement |
|---|---|---|---|
| Cost | ✓ Starting at $124.99 | $2,000+ | $150 |
| Strength (PSI) | ✓ 21,000 | 25,000 | 8,000 |
| OEM Cooling | ✓ Yes | Yes | No |
| Machining Required | ✓ No | Extensive | No |
| Cure Time | ✓ 24 hrs | N/A | 24 hrs |
| Chemical Resistant | ✓ Yes | Yes | No |
| Daily Driveable | ✓ Yes | Yes | Limited |
| Thermal Expansion | ✓ 1:1 with Aluminum | 1:1 with Aluminum | Expands/Shrinks |
Frequently Asked Questions
EJ257, EJ205, and FA20DIT build questions answered.
Yes. EPOXY54 is fully compatible with the EJ257. It uses open-deck aluminum block construction and is one of the most common applications for EPOXY54. The kit includes written and video instructions covering both partial fill and dry-block configurations.
Yes. The FA20DIT also features open-deck block construction and is fully supported. On high-boost FA20DIT builds, bore distortion is a genuine reliability concern — EPOXY54's 21,000 PSI structural epoxy eliminates that flex without requiring a machine shop.
Yes, with a partial fill. The partial fill configuration retains your OEM coolant passages, keeping the engine fully streetable and daily driveable. EPOXY54's thermal expansion matches cast aluminum 1:1, so it moves with the block through normal heat cycles. The dry-block configuration is for track-only builds.
A traditional closed-deck conversion costs $2,000+ and requires a complete engine teardown and machine shop work. EPOXY54 achieves similar bore reinforcement for $159.99, applied in your own garage with no special tools. Rated at 21,000 PSI, backed by 1,000+ proven builds with zero failures.
No on both counts. EPOXY54 is non-expanding and non-shrinking, so piston clearances are unaffected. The partial fill preserves OEM coolant passages and maintains normal cooling capacity. Only the dry-block configuration eliminates internal coolant flow — intended for track builds where maximum reinforcement is the priority.
Neither. EPOXY54 is dimensionally stable after the 24-hour cure. Its thermal expansion coefficient is matched 1:1 to cast aluminum, so it moves in sync with the block as the engine heats and cools rather than working against the bore walls.
Build Your Subaru the Right Way
21,000 PSI. No machining. 1,000+ proven builds.
Shop Subaru Kit →Questions? Call (604) 809-7398 or email support@epoxy54.com