Partial Fill vs. Dry Block: Which Option Is Best for Your Engine?

When it comes to reinforcing an engine block, two common methods are partial fill and dry block. Both serve the purpose of strengthening cylinder walls under high horsepower, but they work very differently—and choosing the right one depends on your build.

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What Is a Dry Block?

• A dry block means the coolant passages are completely filled.

• With no coolant running through the block, the engine relies solely on the head, external cooling systems, or short drag passes to manage heat.

• This is common in drag racing, where engines only need to run for seconds at a time.

Pros:

• Maximum cylinder wall strength.

• Eliminates coolant-related failures.

• Best for extreme horsepower builds.

Cons:

• No cooling through the block → not suitable for street cars or endurance use.

• Requires extensive cooling system modifications.

• Not forgiving if you plan to drive longer than a quarter mile.

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What Is a Partial Fill?

• A partial fill (like with Epoxy54) reinforces the lower portion of the cylinders while still allowing coolant to flow through factory passages.

• This mimics a closed deck design found in modern performance engines.

• Coolant continues circulating, so the engine stays streetable.

Pros:

• Stronger cylinder support without sacrificing cooling.

• Works for both street and track applications.

• Mimics OEM closed deck solutions at a fraction of the cost.

Cons:

• Requires careful installation to maintain coolant flow (see our install guide).

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Which Option Is Best for Your Engine?

• Street cars / Daily-driven builds → Partial fill is the clear winner. You get durability and cooling, keeping the car reliable for everyday use.

• Track cars / Mixed use (street + track) → Partial fill again provides the balance between cooling and strength.

• Dedicated drag racing (high boost, short runs) → Dry block is ideal since cooling isn’t a concern and maximum strength is needed.