1972 chevy 1/2ton pickup overheating, not sure why?

[GuyO]

Hi, I know this is an old thread but ... someone else may have what appears to be an unsolvable heating problem. I had something similar happen to me years ago and the normal fixes didn't work (e.g. radiator, thermostat, hoses, shroud, etc). What it turned out to be was a missing plate behind the water pump. When the water pump was replaced by a mechanic, the new pump didn't have the plate so the old one was discarded. Some 350's have a molded sheet steel plate that mounts to the block and the pump mounts to it. The plate helps the pump to build pressure and directs the coolant to circulate correctly.

It was very strange because some 350's had the plate, and apparently others did not because even the GMC dealer was in the dark. Once I found a plate at a junk yard and installed it, the problem was solved. Good luck! GuyO.