I have a rebuilt 283, almost completely stock, recently installed in my '55 Studebaker Speedster. It runs hot, about 240 F in normal driving conditions. I thought at first it maybe was the gauge, a fairly new SW mechanical unit so I replaced it with a very little used electric SW gauge, same result. Then I noticed if I checked the temperature of the engine right after driving with a infra-red monitor (I used two different kinds), the temp. at the sender was around 200-210 F, The heads were about 215 but the radiator (a fairly new aluminum) was about 195 F. I am using a 14" puller electric fan. Anyway, I drained the system, ran a coolant flush, replaced the thermostat with a new 160 F unit, installed cooling fins near the radiator, new coolant with "Water Wetter" added. Same results with gauge (240) and infra-red temp. monitor (200+). I am told that the infra-red units are quite accurate. So why is the water temp. indicating 240 F?
I bought a cheap gauge set once. I believe it was Omega. Any way the temp gauge read about 30 degrees too high. I called customer support and told them the temp gauge reads 30 degrees too high. They said to put a resistor in the line to the sender. This has been a few years ago and I have CRS, but they told me what value of resistor to use to change the gauge 30 degrees , but I can't remember what it was. So it is possible to correct a gauge if it is off. Have you tried putting the sensor in boiling water?
The temp gauge is immersed in and reading the temperature of the coolant; the infra-red gun is reading the temperature of the metal of the head, intake manifold or thermostat housing (wherever you measured it), that's not the same thing. The temperature of the metal may not be the same temp as the coolant.
Great feed back. Cooler plugs good suggestion. Cooling fins are inserts to otherwise heater hose, they do register a cooling effect with the monitors, the water temp. gauge reading 240 F is significant. If there is a differential between metal and water, then 240 F would be considered normal, but it isn't.
Take cap off radiator with it running, make sure water pump is throwing water out the top and not spinning the wrong direction.
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