A properly operating thermostat only brings the engine to the temperature rating of the thermostat. A 170 deg thermostat opens when the engine coolant reaches 170 deg. If the engine runs hot then it is not the thermostat's fault... you have other issues. Radiator stopped up, hose collapsing on the inside, faulty waterpump etc.

My 54 3100's 235 has a 180. Yesterday I drove 20 miles 60 mph. Outside temp was 92 at 85% humidity. The engine temp didn't quite reach 190.

~~ Jethro
1954 3100
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1951 3100 (gone) / 1956 4400 (still in the neighborhood) / 1957 6400 with dump body (retired) / 1959 3100 panel (in the woods junked) / 1978 Custom Deluxe K10 / 1993 S-10 4.3 / 2004 Chevy Crew Cab / 1945 John Deere H / 1952 John Deere B / 1966 John Deere 2510 / 1967 John Deere 1020