Well just a little info on how the t-stat works. Some 60's Mopars came factory 195 n some 180. A 195 "starts" to open at 195 and completely open at 210. 180 "starts" at 180 n fully at 195. 210-220 at idle w a/c in extreme heat is normal. When it is in the high 80's here, it idles at 198 for an hour. Here's where the needle is at 219°. No boil over, no puking once turned off etc.. no clattering or dieseling when shut off.
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I'm well aware of how thermostats work, thanks - but there's nothing "normal" about an engine designed
in the 60's or 70's running 220F. They simply were not designed for that.
Now modern engines? Different matter - they're designed with all manner of closer tolerances, higher efficiencies
and are meant to run hotter.