ok i got a 87 tbi 350 i overheated several times on accidnet cause i couldnt find my leak stopped the leak .( heater core ) drove once no problems drove again and it overflowed into the, well overflow of course.any way siphoned it out put it back in the radiator drove to the lake had some high temps not to bad. next day i drug my buddys jet boat for him had overheating problems popped the radiator cap and she was dry barely nething in the over flow so i refilled. ok now lets stop here real quick, i got to thinking water has no where to leak externaly. its not in the oil pan and not in the overflow so i ethier got a blown head gasket or a cracked head so i go to do a compression test, spin the motor over all plugs out and number 7 just pukes oil out. so yea i think its rebuild time.