The Stovebolt Site Forums The Shop Area Engine Shop Thermostat question.

Is it best to have a 165-degree thermostat or a 180-degree year-round? I have a 1954 chevy 3100 with the original engine and an aluminum radiator. It has a T5 transmission and 2.73 gears so I drive it at highway speeds up to 70 mph.

WEbold I run 180 the year around but I have the big radiator in a51 6400. Is OK to run warmer if you don't overheat like in a traffic jam. At hiway speeds your getting plenty of air flow.

The only thing a thermostat does is establish the minimum operating temperature of the engine. It's a lot more important to have a clean cooling system with an efficient radiator to keep the max temp under control. A 160 will make you a popsicle if you plan to drive in the winter- - - -virtually no heater output. I'd suggest a 180 to get the internal parts like piston skirts expanded properly to avoid noisy engine operation and premature wear from sloppy clearances.
Jerry

The thermostat manufacturer controls/guarantees at what temperature the thermostat will start to open.
The 1954 shop manual says a 180 thermostat starts to open at 174-184. A 160 at 157-65.
The fully open temperature can vary a lot and can typically be 10 to 30 degrees above start temperature.

GM typically installed 160 at the factory (covers a larger range from the hot desert to cold mountains).
180 is also fine on these old engines.
A 195 thermostat is only for today's fuel efficient, low emissions and high tech automobiles.

Thanks all. My truck seems to be running a little hot lately. I have a small fan because of clearance issues. I have never had overheating issues even on long trips like to KC and back in 95-degree temps. But lately, it seems to be running a little hotter. It is a new thermostat, last summer.

Fix the "issues" and put a real fan on it.
Jerry

First try a new thermostat. Some of the ones we get now are junk. Check the pressure cap to make sure it is holding pressure. Try the simple things first.

Just wanted to add that one of the worst things you can do to an engine is run it cold. 190 to 210 is a fine operating range for coolant (antifreeze mix). Excursions to 220 in certain circumstances are not bad.

Also - remember internal combustion engine is a heat engine that runs at poor mechanical efficiency. When you timing, mixture or compression is off your efficiency drops which means less mechanical energy and more heat energy - thus overheating when cooling system can no longer handle the situation.

Thanks, Stoucthon, that was the answer I was looking for. The temp has never gone over 200. I m not really sure even that much because it has an after-market sender which I was told reads too high. Jerry, it has a real fan and an electric one which is controlled by a switch under the dash. It has only overheated once and that was 14 years ago and that was because the radiator was the original one and it was plugged to stop leak and then sat for 2 years while the bodywork was been done.

If the coolant isn't boiling, the engine is probably not "overheating". A 15 pound radiator cap with a modern radiator and heater core capapble of holding the pressure raises the boiling point of the coolant to 257 degrees F.
Jerry

You could borrow an IR thermometer gun and check different points on the block and head.
Use the readings to determine if there is anything to worry about.

we used to get hot in slow traffic or stop lights when the temp got over 90 outside.
the fan it only there for when you are stopped or not moving fast. once you are at speed. the fan it basically not doing much as your pressure wave is really pushing air thru the radiator.
Instead of trying to adjust radiator types and thermostats. The all purpose properly fitted shroud solved all the slow stopped traffic issues. temps stayed where they were supposed to year round.
with 180.

I bought one of those thermometers, did not work too well, and sent it back. Probably went too cheap.