I'd say Stuart's right, FWIW - there isn't really a 'supply line', the heater flow is just a loop - the valve restricts the flow in the loop so that the water that goes thru the core is slower/faster
if bill1949 has freshly rebuilt parts, the right hookup, both hoses on the valve hot and the one from the core cold, I'd suspect that the freshly rebuilt core has a solder plug preventing flow
the test would be simple - remove hose at point C and plug that at the engine, see if water comes out the hose
if you can make up a simple fitting you can also take both hoses off the core and put yer garden hose to either core tube and see if water flows thru it ..... case closed
Bill
