I am getting heat out of my heater any time the car is moving. Upon investigating, I have found that my universal cable-operated heater valve can easily be blown through in either direction when fully shut. The valve is located in the line from the intake manifold port to the heater core; it enters the lower heater core port. The upper heater core port flows to the fitting on the water pump. I believe this is the correct setup, so I believe the closed heater control valve must be flowing enough hot water to keep the core hot.

Can anyone recommend a cable-operated valve that completely stops the flow when shut?

1954 Crestline Victoria 312 4-bbl, 3-speed overdrive