My old 216 engine used to creep up to 210 + degrees on extremely hot days but to my knowledge, never boiled. I do NOT have a Science /Physics degree but it appeared to me that it took an entire Bunch more of energy to make it boil. I am running the new to me 235 engine with a 180 therm. Same radiator and it runs at a very steady 180 degrees unless I drive it extremly hard, it may go up to 185 degrees! I know this 235 block is clean, I think old 216 block had some crud.
Jerry


Jerry