OK..GOT A 1968 WITH A 289...WAS DRIVING IT BACK FROM L.A. AND IT STARTED OVER HEATING ON ME, AND I MADE IT TO SANTA MARIA BEFORE I HAD TO GET A TOW. THE HEATER BLOWS WARM AIR BUT NOT HOT. SO IM THINKING ITS EITHER THE HEATER CORE OR THERMOSTAT I HAVE HAVE TO REPLACE OR BOTH. AND AS WELL IT DOESNT WANT TO START IN THE MORNINGS....ANITFREEZE GOT ALL OVER EVERYTHING IN THE ENGINE COMPARTMENT(DIDNT HAVE MY PRESSURE RELEIF HOSE ON) WHEN IT OVER HEATED.
ANYBODY OUT THERE HAVE ANY OTHER IDEAS AS WHAT TO THE PROBLEMS COULD BE OR WHAT ELSE COULD BE WRONG?

 

do a pressure test on teh cooling system and see if you have any leaks. I would lean toawrds the thermostat like you mentioned if the system doenst loose pressure. Also do you have any type of under drive pulleys on it?

 

one other thing i forgot to mention is it can have a cloged passage way. with teh car cold open teh radiator cap and than turn on the car and watch for the coolant to circulate.