Thermostat Housing

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The thermostat housing (also called a water outlet connection in the master parts catalogs) used on 428 Cobra Jet engines is a cast aluminum piece that was also used on other FE engines of the same vintage. The 1975 Master Parts Catalog identifies the housing using service part number C4TZ-8592-C. An engineering number of C8AE-8594-B is cast into the top of the housing. The housing includes a threaded hole used to mount a distributor vacuum control valve and two holes used to mount the housing to the front of the intake manifold.

Thermostat HousingThermostat Housing, Side
Thermostat HousingThermostat Housing, Side

The housing is designed for use with one of two thermostats: a 180° "low temperature" thermostat (service part number A8AZ-8575-B, Motorcraft sales number RT-8) or a 190° "high temperature" thermostat (service part number A8AZ-8575-C, Motorcraft sales number RT-9). Both measure 2 1/8" in diameter. Replacement thermostats are available from manufacturers like Stant in several different temperatures, including 160°, 180°, and 195°.

Thermostat Housing, Back

As shown in the picture below, the engineering number cast onto the top of the housing may be difficult to read, with the "B" appearing more like a "D" or an "E". Note that there are at least two different versions of the engineering number casting. On one version the engineering number appears on two lines. A second version, marked "Sheffield" and with the engineering number along one horizontal line, has also been observed. Thanks to Joe Valenti for the picture of the Sheffield version.

Thermostat Housing Engineering Number Variation 1Thermostat Housing Engineering Number Variation 2
Engineering Number Variation 1Engineering Number Variation 2