Water temperature

[MYBAD79]

When I installed my AutoMeter gauges I noticed that I have to drill and tap a hole in the head for a 1/4NPT metal temp sensor that came with the cyl head temp gauge... well ... I was lazy and simply screwed it into the water temp plug on the passenger side. My water temp gauge is located at the front of the intake.
Turtle asked a few weeks ago if there's any difference between the two locations and I thought there wasn't....
Now I drove the car for 40+ miles and noticed that the temperature measured at the front of the intake manifold is 10 degrees higher than the other gauge reads at the cyl head....

I kept it at 2400 rpm in 4th gear and the temps went up to 190/180, I shifted in 5th and the temps went down to 180/170....

Thought hat was interessting... maybe I add a few more gauges to completely confuse me.... :bonkers::beer:

 

[Twin_Turbo]

Water temp plug on passenger side? of what? The manifold? Do you have a water temp and a cyl. head temp gage? I'm confused here.

 

[MYBAD79]

Water temp plug on passenger side? of what? The manifold? Do you have a water temp and a cyl. head temp gage? I'm confused here.

Yes, one is a water temp gauge, the other is for cylinder head temp.

Eventually I'll install the cyl head temp feeler correctly, right now it's measuring water temp at the rear of the passenger side head. There is a (estimated size) 3/4" NPT thread in the head, I installed a reducer to allow the 1/4 water temp sensor to be installed here.

The original sensor for the water temp gauge was installed in this location...

What's the better location to measure water temp ?

 

[Twin_Turbo]

For water temp the thermostat housing or the front coolant crossover. Head temp, original location on either head is fine.