ben442

68 442, 455, 2000miles on fresh engine rebuild, new 3 core rad with clean fluid, 165 thermostat. rally pac gauges.

Engine running - With a digital laser infrared thermometer the radiator temperature from top to bottom is in the range of 185 to165. My temperature gauge needle is about 3/4 of the way up.

Should the gauge be so close to the top with those rad temp numbers?
Do the lines of the temperature gauge represent a specific number,(temp)?

… Ben

VC455

An instrument technician told me the gauge inaccuracy problem was usually with the sending unit.

Aftermarket senders sometimes have a different range than the OEM units.

And I seem to remember that even some GM units were different, specifically the ones on the GMC Motor Homes.

Are you measuring temperature at the outlet of the upper hose?

ben442

Yes measuring rad temp at the upper hose outlet 185, 165 where rad fluid exits back to engine.

rustyroger

Doesn't sound like your radiator is very efficient. Do you have a fan running when you check the temperatures?.

Roger.