1st no more than 25%
antifreeze, you live in Tx maybe a little less.
2nd do you have a filler just above your t-stat outlet? If so you should have the highest rated cap 18-20 lb there. The radiator should have a lower rated cap 16 lb. Your overflow tube should come off the radiator to the bottom of the over flow tank. From the top of the over flow tank you should have a tube to the lower part of the tank/car (for overflow). Maybe this picture will help.
3rd correct size/type radiator. A six cylinder radiator might not cool your 347.
4th do you have a adjustable fan control? is your fan large enough to cool you motor. Most fans are bought at Auto Zone and are not sized for the motor. Your 347 is bored .030" over and will run hotter than a stock motor. But with the pumbing hooked up correctly to the over flow, right size fan, correct anti-freeze mix and the correct radiator caps it will run cool!
Dwight
