I have 1934 pfxx Plymouth that over heats. I have flushed block and radiator with radiator flush chemical, changed the thermostat and it still over heats. I preformed a block combustion test and it did not indicate a problem. Any ideas? thanks

 

Faulty radiator cap or water pump belt loose?
Timing it correct? Not over fuel it's self is it?

 

Could be a collapsed radiator hose while under load too. Once you kill the engine they go back to normal so its difficult to pick up on.