VCCA Home Forums TECHNICAL - 1945 AND EARLIER 1937-1945 Operating temperature of a 235 engine

First of all..I have a 0 pressure radiator cap. The gauge reads about 135 degrees driving down the road. I'm sure it is hotter than that. Maybe the temp gauge needs calibrating. What should the ideal temp read driving along about 50mph ?

My 235 runs (according to the stock temp gage) around 170°F when cruising along at 50mph on a day with an ambient temp of 75°F or so. Most gasoline engines run most efficiently at
160°F - 190°F.

Assuming you have a mechanical temp gage, stick the probe in a pot of heating water, along with a thermometer of known accuracy. Heat the water to 212°F according to the thermometer and note if the temp gage follows. If it doesn't get it repaired or replaced. If it does, check your thermostat for operation and temp rating.

A pressure radiator cap will raise the boiling point of the coolant approx 3°F / pound of pressure (i.e. a 5 pound cap will raise the boiling point to approx. 227°F).

In this "mild" weather is should run at what ever temperature the thermostat that is installed is rated for. I run a 160 degree in my cars as winter heat is not necessary. They run at 160 unless the outside temperature is above 80 degrees or so. Then will run warmer.
If you have no thermostat it will run at about 135 Deg at this time of the year in your area. The best way to check the actual temperature is with a non-contact temperature gun with a red laser site. This is a very intresting devise and can be used for many automotive applications.
With no thermostat the engine will take about 15 minutes to get up to normal operating temperature. With the thermostat it will be up to mormal in about 5 minutes. It is best to run a thermostat. The 1938 thermostat fit Chevrolets up into the '90's and are easy to find.