I have a simple cable operated on-off valve to shut the water off to the heater core. The problem I have is that the truck will overheat unless the valve is open. This means that I have to run with the heat on at all times which is not pleasant in the Summer.

SO, I could replace the simple valve with a bypass valve of some sort like this:
https://www.amazon.com/dp/B07H5DCS7H/ref=psdc_15723841_t3_B004AF34DQ

OR I could get a pressure operated bypass valve like this:
https://www.amazon.com/dp/B004AF34DQ/ref=psdc_15723841_t3_B07H5DCS7H

I like the looks of the pressure operated bypass valve.

Ideas welcome!

Note that I have the 261 style thermostat housing with a Stant 13928 thermostat. This setup seems to work fine as long as there is coolant flow from the underside of the thermostat, through the heater and back to the water pump. I'm assuming that the heater core does not provide enough cooling to keep the temp gauge needle in the middle!

Gord 🇨🇦
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1954 1/2 ton 235 4 speed