[franky 455]

I have a sender from an Autometer Gauge in the passenger side head and now I have installed a Holley Sniper EFI I had to put a sender in the intake manifold for the computer and it is 18 degrees cooler there, which is the correct spot.
Cheers Frank.

[franky 455]

Here is some pictures around 65mph on a hot day.

[Squidward]

I think your setup is good. My understanding of the EFI is that the temp sensor functions mostly binary - either at normal operating temp for closed loop, etc, or it is still cold. This would make the crossover the perfect place for the EFI temp sensor. I think you are good with your gauge reading the higher of the two so you can be fully aware of any "oh no" moments of excess engine temp.

FWIW, I run the temp gauge and the EFI sensor from the water crossover on both of my cars. I run 1969 and 1970 heads, which don't have the head sensor provision.

[franky 455]

I know everyone says over 200 deg. is still ok but I don't really like it, I read somewhere that an idiot light will come on at 280 deg. is that correct?

[Peter Serio]

As I recall the threshold for closing of the internal contacts of a coolant temperature over heat warning lamp switch in GM cars (built in the 1960s and 1970s) is right around 242 or 243 degrees Fahrenheit.

[JLMounce]

The difference in fueling calculation between 18 degrees of water temp is going to be negligible for the system. The only time you would need to worry about the disparity here is if the temperature was not passing the threshold for learning and closed loop operation. I'm not sure what temp that is for the Sniper, but the FiTech is 150 degrees.

What is occurring with the water temperature is to determine the approximate cylinder temperature. The software takes the coolant temperature and compares it to the intake air temperature to determine cylinder temp. Since these two temperatures are used as a ratio to determine the cylinder temp, minor disagreements don't produce major swings in fueling. Long story short, don't worry about it.

[franky 455]

Yes I would have thought 280 for the idiot light was a bit extreme, I think by then there would be other signs that your too late. Thanks for the help, I will stop worrying. Cheers.

[Pepi]

For what it is worth, for my 73, the GM Service Manual says the light will come on when coolant reaches temperature of 248°F ± 20°F.

[64speed]

I want to run my idiot light my temp gauge and I have to run the sensor for the fuel injection and there are only two ports in my water cross over. I plan to do like you and put my temp gauge in the drivers side head. I was told from the outset that it would show hotter but that’s ok as long as I have my idiot light to draw my attention in the front port.

[dlloyd]

Where in the head did you put the sensor? Can you post a picture? Thanks, David