Checking temp with a Ifrared temp gun


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By Talkwrench - 12 Years Ago
Would it be normal for temp to be hotter on the outside of the engine? Trying one of those ifrared temp guns,my temp gauges [on my flathead ]saying cooler inside Im pointing the gun at right where the senders are in the block outside.. Quite a bit of difference ..??
By Frankenstein57 - 12 Years Ago
I found that reading to be 10-20 degrees higher than the temp gauge. No surprize as the coolant is moving through pretty fast
By Talkwrench - 12 Years Ago
Yup I was getting readings in the 20+ Difference.. It did become hard to read at times as the thermo fan kicked in air bounced around my figures.. Was a cheapie tool, thought it would give me an idea though..
By Ted - 12 Years Ago

Those infrared temperature guns are sensitive to the material that they are pointed to. Being shiny versus satin finish versus being painted will make a variance in the temperature readings. The higher priced infrared guns will have the ability to custom tailor the readings to the material or the reflective finish being measured for temperature.
By charliemccraney - 12 Years Ago
You're also relying on the accuracy of the sender, and gauge and that is not always too great. The gauges are really best for determining if the temperature is different than normal, rather than the precise temperature at any given time. The temperature at the sender will very likely be lower than the thermostat rating as well, because the coolant has 3 more combustion chambers to cross over before it is fully heated.
By Macs1964F100 - 12 Years Ago
Why did Ford not put the temp sensor at the front of the head? My 64 292 reads 150 degrees even on a 100 degree Texas day with a 180 thermostat. I have a new thermostat to install. 180 seams like a more appropriate temp. I have checked the connection to the sensor and the gas gauge is correct.
By Ted - 12 Years Ago
Macs1964F100 (9/22/2013)
Why did Ford not put the temp sensor at the front of the head? My 64 292 reads 150 degrees even on a 100 degree Texas day with a 180 thermostat. I have a new thermostat to install. 180 seams like a more appropriate temp. I have checked the connection to the sensor and the gas gauge is correct.

It’s difficult to double guess what the engineering was thinking in regards to the temperature sensor location back in the day but the selected location was likely just the most economical and vehicle friendly location at the time. While it’s a given that the temperature reading will be less at the back of the head versus being located at the front closer to the thermostat, any heating issues are still evident but simply at a lower temperature reading on a gauge that actually shows degrees.

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But if there is a conspiracy theory involved, then the rear temperature sensor location could have been picked intentionally simply to give an arbirtrary cooler reading to offset some of the bad press the Flatties received in running on the ‘Hot’ side.

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When dyno testing Y engines, I typically always use the location just behind the thermostat for temperature readings. It is more accurate from a testing standpoint. When installing fuel injection units on the Y engines, I find that relocating the temperature sensor to the front of the engine also works better.