413 overheating or bad gage?

[3175375]

BTW, you think a T-fitting could work to fit a larger probe??

You can use a tee to physically connect the sensors to the block, but be careful.
The mass of the sensors and adapters, fittings, etc. may cause undue stress on the pipe coming out of the block and crack. Don’t ask me how I know...

 

[Ripinator]

Check your sending unit with an ohmmeter. Original sending units are as follows as would have been seen on the original gauge low first line should be around 74 ohms. Middle line around 23 ohms. Hot mark all the way to the right should be 10 ohms
So if your sending unit is reading lower than 74 ohms give or take 10 ohms it is likely your sending unit.
Check again when your thermostat first opens. (You will feel heat in the top radiator hose and radiator). It likely should read around the 23 ohm mark. If it is reading lower,more than 4-5 ohms less than 23 ohms, your sending unit may be reading high. Make sure your thermostat is opening at around the 180 degrees or whatever value your thermostat is.
Sorry I don’t know the exact table of ohms to degrees. Just going off factory gauges.

I would add one more thing here: Make sure you even have a thermostat. It could have been removed by some previous owner thinking it would help to cure an over-heating issue. When I had to replace the water pump in my '66 300 coupe, I discovered the thermostat was not there. I installed a new one, and was surprised that not only did the car run cooler, but it also ran better, because it now ran at the correct engine design-temperature

 

[Drew-Pritchett]

Yeah its hot here lol, but about to move a little more north.

I might fix, just need to find some r12!

 

[live4theking]

Make that '66 and newer. . .

Rip,
My 68 NYer doesn't have that small port on the driver side. It is on the passenger side and comes in horizontally in front of the heater hoses.