1960 big twin 40 ball at bottom of thermostat housing?

[nahoo7]

So I removed the thermostat cover to check the thermostat, it has seized open so will need replacing.Thing is the centre of the top of the thermostat has been removed so I am guessing since it doesnt get that cold here in australia a previous owner modified it instead of replacing it.My question is is the thermostat supposed to push down on the plastic ball at the bottom of the chamber to allow more water to circulate through the head because on measurement the thermostat although seems to be fully extended doesnt reach to depress the ball.Would it be the wrong thermostat in there and is the ball supposed to be pushed down during operation? many thanks.

 

[kodibass]

Re: 1960 big twin 40 ball at bottom of thermostat housing?

I do not think the t-stat does anything in regards to the spring & ball. water pressure after starting the motor is circulated thru the jacket & 1 pound of water pressure against the ball pushes the spring down and recirculates water back to the water pump. then when the motor reaches operating temp about 130-150 degrees the t-stat opens sending most of the water thru the exhaust outlets both above and below the waterline. (I think?)

 

[nahoo7]

Re: 1960 big twin 40 ball at bottom of thermostat housing?

thank you for clearing that up for me kodibass.

 

[F_R]

Re: 1960 big twin 40 ball at bottom of thermostat housing?

kodibass got it right. When the thermostat is closed, water pressure opens the ball check valve for recirculation. When the thermostat is open, the check valve remains closed, preventing recirculation. If I may add something to that, too many people think they can remove the check valve. Not a good idea. Without the check valve, exhaust can flow thru the open hole, go down to the water pump, and prevent pumping. It is a great water pump, but a lousy air pump.