There may be more to the OP question then most would think.
It was not until 1948 that Chevrolet introduce a bypass path in there engines to keep water flowing when the thermostat is closed.
If you look at the front of the block where the pump mounts, you will see, besides the main water transfer holes, an extra hole which only goes into the block a short distance, then turns up through the head gasket and into the head water jacket. This circulated water just through the engine and head when the thermostat was closed.
Of course this is only important on heater delete vehicles, which a lot were in those days.
Chevrolet must have added this bypass for some reason...
I do not know if an original 1947 or earlier thermostat had a small bypass designed into it, but it may have, which would accomplish the same thing.
