TB coolant line is the best location by far. Easy install. No drilling and tapping. Acurate readings all the time, not just after t-stat opens. Easy to remove if you want.

 

As it turns out, the wiring was the issue. The line I had tapped for the gauge ground turned out not to be grounding at all. The autometer tech suggested I check that as he says the gauge will still work, just appear to be too high.

Water Temp Gauge is working just fine now. For anyone else with the same issue, double check that guage ground.

Thanks for the help in getting this solved.

Now time for the Koyo radiator, new coolant hoses, and aliminum ast install and the FD has a new and improved cooling system.

 

Good read. I have the exact same problem. I bought my FD as is with an autometer water temp gauge. It rises and falls drastically. At start up it reads around 100 degrees. If I start it back up after a quick stop, it rises real fast and reads "HI" then after a few minutes falls back down to "LO" and go up to 180 - 190 where it fluctuates. Guess I'll have to do some checks on the wiring.