MMI Thermostat, 150 degree (late model double-acting)

This is the last thermostat you should ever need. Manufactured using brass and stainless components it was specifically designed for the late model Atomic 4. This thermostat is basically designed as a replacement for the original Holly “three spring thermostat”.  The unique conical design of its main valve simultaneously begins to attenuate the flow of by-passing water as the thermostat opens to allow the flow of hot coolant to flow up from the block and head.  This makes it a true “double-acting” thermostat.  This design also eliminates the need for any additional restriction in the by-pass loop.

In raw water cooled systems, temperature will typically settle in between 160 to 175 degrees depending on the overall condition of your cooling system, and the temperature of the raw water. This thermostat can also be used in fresh water cooled systems, in which case the operating temperature may be slightly higher (170 to 185 degrees) due the capacity and condition of your heat exchanger.

Like the original Holley, this thermostat is designed to work with a standard late model thermostat housing with no need for a spacer.  If you chose to use a spacer for any reason, be sure to mount this thermostat on top of the spacer.  If there’s already a manual valve in your bypass loop, you can also leave it installed and simply place it in the open position.

Gasket included

(CSTH_589)

Manufactured in the USA