Are you referring to a 2nd series 1955 235 truck engine in a 1952 3100 truck?
What psi radiator cap are you using?
" . . it has the older water pump on it and the fan sits low . . " The older 216/235/261 water pump sits higher than the newer 235/261 water pump.
What is the code pressed into the block in the ledge to the rear of the distributor?
