GM LS / LSX Closed Deck Conversion | EPOXY54

GM LS · LSX · LS1 · LS2 · LS3 · LS7 · Open-Deck V8

LS engines are legendary — light, powerful, and swap-ready. But aluminum LS blocks are open-deck, and builders running serious boost have been stuffing Portland cement into the bottom of the water jacket for decades trying to solve it. EPOXY54 is the purpose-built epoxy that replaces the concrete workaround for $299.99, with 21,000 PSI compressive strength and zero mess.

21,000
PSI Compressive Strength
$299.99
V8 Kit Price
24 hrs
Cure Time
DIY
Friendly · No Machining
Why It Matters

The LS Block's Open-Deck Problem — and the Concrete "Fix" That Isn't

Aluminum LS blocks from LS1 through LS3 are open-deck. The cylinder walls are unsupported above the water jacket. Under boost, this is where builds fall apart — and the community's answer for years has been to fill the void with something. That something was Portland cement.

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Cylinder Wall Deflection Under Boost

Without lateral support at deck level, open-deck LS cylinders can flex outward under sustained high-boost combustion pressure. This breaks ring seal, accelerates bore wear, and eventually distorts the cylinder enough to cause oil consumption and blow-by — even on otherwise healthy builds.

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The Concrete Bottom-Fill Problem

The LS community's DIY workaround is to pour Portland cement into the bottom of the water jacket, letting it harden as a support base. The problem: cement doesn't bond to aluminum, it shrinks as it cures, it can trap moisture, and if it shifts or cracks under vibration, you've got loose debris in your cooling system.

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EPOXY54: Purpose-Built for the Job

EPOXY54 bonds directly to aluminum and cures to 21,000 PSI — higher compressive strength than concrete. It fills the open water jacket at deck level, eliminating cylinder deflection at its source, without the shrinkage, bonding failures, or debris risk of cement.

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Cheaper Than an LS Block Rebuild

A blown LS on a boosted swap is a $2,000+ problem when you factor in machining, pistons, rings, and downtime. CSS kits for LS applications run $800–$1,200 before any machine work. EPOXY54 costs $299.99 and you do it yourself over a weekend.

Installation

How to Close-Deck Your LS Block

The same process used across all open-deck LS variants — LS1, LS2, LS3, LSX. Done with the engine out and heads removed.

1

Prepare the Block

Engine out, heads removed. Fill water jacket with a water-soluble temporary solute (sugar or salt solution) to displace the area you're not filling.

2

Mix & Pour EPOXY54

Mix the two-part epoxy to a runny, pourable consistency. Fill the top ¾" of the water jacket at deck level around all eight cylinders.

3

Cure for 24 Hours

Let the epoxy cure fully at room temperature. No heat, no machining, no press — just time.

4

Drill Coolant Passages

Once cured, drill coolant passages back through the epoxy following the head gasket layout, maintaining critical cooling paths.

5

Dissolve & Flush

Flush out the temporary solute with water. Inspect, reassemble, and you're done.

How It Compares

EPOXY54 vs. Concrete Bottom-Fill vs. CSS Kit

The three options LS builders actually discuss — with honest trade-offs.

Feature EPOXY54 Concrete Bottom-Fill CSS Kit (Machined)
Cost $299.99 ~$10 (Portland cement) $800–$1,200 + machining
Compressive Strength 21,000 PSI ~4,000–6,000 PSI 6061-T6 aluminum rings
Bonds to Aluminum ✔ Yes ✘ No — sits loose ✔ Pressed fit
Shrinkage / Cracking Risk ✔ None ✘ Yes — shrinks on cure ✔ None
Debris Risk to Cooling System ✔ None ✘ Yes if it shifts ✔ None
Machining Required ✔ None ✔ None ✘ Yes — shop required
DIY Friendly ✔ ✔ ✘ Shop only
Thermal Expansion Match 1:1 with Aluminum Mismatched 1:1 (aluminum rings)
Cure / Lead Time 24 hrs 48–72 hrs 2–3 weeks (shop queue)
FAQ

Common Questions — GM LS & LSX

Straight answers for LS builders running boost.

The aluminum LS1, LS2, and LS3 blocks are open-deck. The iron LS blocks (like the 4.8L and 5.3L truck motors) are closed-deck from the factory and don't need the treatment. The LSX454 and LSX376 are purpose-built race blocks with closed-deck architecture. If you're running a boosted aluminum-block LS swap, you're working with an open-deck engine.
Portland cement doesn't bond to aluminum — it simply sits in the void. As the engine heats and cools through thousands of cycles, the cement can crack, shift, or break apart. Loose pieces in your cooling system will clog passages and damage the water pump. It's a budget workaround from an era before purpose-built options existed.
Yes. The process is applied at the block level — it doesn't matter whether the LS is in a Camaro, a Miata swap, a truck, or a standalone build. You're working on the bare block with heads removed, so the chassis is irrelevant.
No. After EPOXY54 cures, you drill coolant passages back through following the head gasket layout. The critical cooling paths are preserved — you're only eliminating the structural void, not the coolant flow.
Stock LS builds at mild boost (8–12 psi) with conservative tunes often hold together for a long time. The risk rises sharply with higher boost, higher cylinder pressure from power adders, and sustained track/racing use. Closing the deck before pushing power limits is the move — not after a cylinder lets go.
EPOXY54 is designed to be DIY. No machining, no press fit, no CNC. You need the engine out and heads removed — which you're probably doing anyway if you're adding boost. The pour, cure, and drill process is done in your garage over a weekend.

Stop Doing the Cement Trick

Close-Deck Your LS the Right Way for $299.99

Concrete shrinks, cracks, and doesn't bond to aluminum. EPOXY54 was built for this job. No machine shop, no debris risk, done this weekend.

Order EPOXY54 Now → Ships fast · No machining required