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Old 11-15-2010, 08:10 AM
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Checking Accuracy of Water Temperature Gauge

Hello Folks,

I am in the process of tweaking the cooling system on my 47 Plymouth. The first thing I would like to do is verify the accuracy of the water temperature gauge, which is the stock factory mechanical unit. The engine side of the gauge is threaded into the driver's side cylinder head (350 Chevy TPI engine).

I will be using a hand-held infrared thermometer.

Question - should I check the temperature right at the head, where the gauge is connected? Or should I check it at some other location?

Thanks in advance!
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Old 11-15-2010, 12:20 PM
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I use boiling water.

I put the sensor in boiling water and mark the guage or (make a mental note of it) when it stops going up. That is 212 degrees F.
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Old 11-15-2010, 05:28 PM
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The water temp gauge tells you the water temp throughout the engine, if you shoot the cyl head with the gun it'll be much higher than the water temp. I'd shoot it at somewhere on the block or even the rad tank or a hose.
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Old 11-15-2010, 07:09 PM
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I shoot the manifold right before the thermostat housing. This is my reference temp. I also have a spacer between the thermostat housing and the manifold that gives me a fitting for the heater and sending unit.

I also have a temp sender at the back of the manifold. I'm just getting ready to hook up a wire with a switch in it so I can read either the thermostat sender or the rear of the block.

Be aware that the hand held units have a spot size that varies according to distance. 6:1 is common. You really need to be quite close to get accurate readings. You also need to be consistant distance. Mine has a laser sight that is worthless. It's way off to one side and way high. Good thing I don't hunt with it haha
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Old 11-15-2010, 08:05 PM
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Quote:
Originally Posted by bentwings
I shoot the manifold right before the thermostat housing. This is my reference temp. I also have a spacer between the thermostat housing and the manifold that gives me a fitting for the heater and sending unit.

I also have a temp sender at the back of the manifold. I'm just getting ready to hook up a wire with a switch in it so I can read either the thermostat sender or the rear of the block.
Thanks for all the responses so far.

This is all quite interesting. Am I to understand that I may not be getting an accurate water temp reading, due to the fact that the sender is located in the cylinder head? (Why else would there be access to the water jacket at that location on a SBC?)

The mechanical nature of the temp gauge restricts where it can be connected to the engine; it will only reach to the cylinder head location.

Should I concentrate first on installing a water temp gauge (electric, I suppose) that will allow me to place the sender in a more accurate location, perhaps at the front of the intake manifold?

Thanks again!
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Old 11-15-2010, 08:35 PM
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simply, yes you should
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