For applications requiring a thermostat to keep the engine at operating temperature, we recommend using a Stewart/Robertshaw high flow thermostat. This thermostat does not restrict flow when open. The Stewart/ Robertshaw thermostat enhances the performance of the cooling system, using any style of water pump. However, the Stewart Stage 1 high-flow water pump may require this thermostat to operate properly, and Stewart Stage 2, 3, and 4 water pumps simply will NOT operate with a regular thermostat because these pumps have no internal bypasses. Stewart further modifies its thermostat by machining three 3/16" bypass holes directly in the poppet valve, which allows some coolant to bypass the thermostat even when closed. This modification does result in the engine taking slightly longer to reach operating temperature in cold weather, but it allows the thermostat to function properly when using a high flow water pump at high engine RPM.

Stewart Components has been a recognized leader in high-flow cooling system technolog for decades, and is currently developing the next generation of high efficiency advanced mechanical and electric water pumps and cooling system components. Stewart Components combines engineering expertise and advanced product development to bring forth innovative solutions. Stewart water pumps are the #1 choice of professional engine builders, race teams and performance enthusiasts, from street rodding and OEM replacement applications, to the most extreme forms of motorsports in the world.

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