The Stovebolt Site Forums The Shop Area Engine Shop 261 bypass thermostat housing question

Mike,

I confirmed the casting codes on base and top of the larger diameter 261 housings:

casting code on the base: 3764748
casting code on the top: 3764749

Also, the thermostat is almost at a boil and you are correct,

There is an internal cup that is open on the sides when "cold".
The cold coolant can easily move through slits around the sides.

When the coolant is hot, the cup moves downwards to almost totally restrict the "open" flow through the side slits/openings.
The heated coolant now moves through the spring-controlled "pellet" center-top-opening (which opens when the coolant is hot).
This opening now regulates flow, thus regulating the temperature of the coolant.

Thank you very much.