326 V8 190 Degree Thermostat

[JoeS]

The shop manuals for the 66-67 Pontiac 326 V8 (as well as the OHC 6 cyl.) call for a 190 degree thermostat. I just replaced one in my 67 Tempest 326, following the book. 190 degrees seems awfully hot for that engine to run. My question is: would a lower degree thermostat, such as 160 or so, hurt the engine performance, fuel/ignition efficiency, etc? Thanks, Joe

[Larry]

While 190-degrees seems pretty hot when comparing to 212 as boiling temperature, remember that the pressure in the cooling system and the mixture of antifreeze with the water (usually about 50-50 prefered) raises the boiling point of the liquid quite a bit.

An engine would have to get quite a bit hotter than that to be a problem with the fuel and ignition... kind of like red-hot where the fuel either boiled away, or the hot metal exploded the fuel before the spark plug could. 190-degrees isn't going to cause that.

About the only thing one might say is that if your cooling system wasn't up to par, a cooler thermostat might help water flow and thus cooler operating temps. But, if all is in good order, hotter (within factory design specs) is actually better than colder.

To be on the safe side, you might want to check with a thermometer to be certain that your thermostat is actually opening at 190 (you can tell because the water will begin to flow in the radiator tank when it starts to open). Then check that your dash gauge (if you have one) is in the right range (usually about 2/3 to 3/4 range).

Bottom line, if you are experiencing good performance, no hint of overheating, and a proper reading gauge, you are in good shape. Let us know if you have any problems or other questions.

Other thoughts on the subject out there?
Larry