I have a '46-'48 Dodge in my '38 Plymouth p6. coupe.
I've had it about a year and drive it everyday.
There is no thermostat, the hose goes into a small housing with no room for a thermostat and then to the radiator.
the water pump I believe is a bypass type with a cap on the outlet.
It runs great and doesn't run hot. How important is it to have a thermostat?
I have a housing that will take a thermostat, should I install it? The car doesn't have a heater.
Thanks, Jim

Do you know what temperature it runs at?

In winter you might get away with blanking off part of the radiator.

Install the thermsotat; your engine will last longer if it is at operating temperature. I can't point you to any right now, but there are charts which plot engine wear vs. operating temperature. It decreases dramatically as you approach 180°C.

i might be mistaken jason, but wouldnt the engine run cooler without the thermostat? the point of a thermostat is to stop the flow of coolant to the radiator, allowing the motor to heat up, and then to open at whatever the set limit is, so the water tempurature wont go any higher than normal operating temp, i.e. 160 or 180 degrees,

but i dont noe what kind of problems (if any)
there would be with running the motot cooler, like metal expansion with heat, etc.

P6'38, if u do install the thermostat be sure to install the thermostat bypass, its there to prevent hot spots inside the block, which can do damage to your valve seats

I have installed the thermostat and it's running about 170- 180 degrees. The bypass is in the thermostat housing and allows water to circulate a small amount until the thermostat opens up.
I agree, the faster the engine gets to operating teperature, the less wear on the engine.
Thanks for responding,
P6'38