I may be sort of a lone wolf, but I ran my fan manually. On cool days, (40's to 50's) once the car was moving at 30mph or more, no need for fan at all. On really hot days of 90+, I turned it on and let it run. The temp gauge would occasionally climb above 200-210 when in slow or stalled traffic. No worries. As previously stated, with a good cap, it won't boil until it hits 220 to 235 or 240.
No, the below boiling water temp does not hurt the engine UNLESS the
oil temp gets high also. Above 250 on the
oil temp is not good for the
oil. It basically cooks it and ruins the lubricating ability.
There is at least one real oil expert in the club....Callling Mr. Parmenter.....calling Mr. Parmenter.....Bob can give the real lowdown on oil viscosity and temperature ranges.
My 427 S/O's oil temp never got above 180, even when the water temp sometimes reached 220 or 230. I credit the 13qt capacity oil system with external oil cooler for this.
I'd say don't worry about the water temp, unless it is consistently running above the 200-210 mark in normal driving. DO worry about the oil temp above 210. Once it gets that hot, it doesn't take much for it to exceed it's operating range and lose it's viscosity and cost you an engine.
Put in the normal 180 thermostat and run with it.
Al