I have a rebuilt 283 in a 1957 Chevy pickup. It has a new short water pump with a Edelbrock intake. I'm using my original radiator (formerly a 261), I installed a fan shroud. The thermostat has been replaced. It overheats, but it appears as if the thermostat is not opening, since the fluid in the radiator never seems to heat up. Also, I get no heat out of the heater, which makes me think there is no circulation. The timing seems to be roughly correct. I'm wondering if I'm getting cavitation in the water pump. I have tried running without the radiator cap initially to remove air pockets. Any thoughts about what I could try next would be appreciated.
