I beg to differ with some of our more experienced contributers. Though it was not a 235, but a 292, I had a crack between #3 and #4 cylinders above the oil gallery that put oil in the cooling system, no water in the oil. I drove it that way for a few thou. I don't remember how I determined exactly where it was, unless it was after the thermostat stuck, then there was water in the oil.
It maybe rare but
Larry
