I have a 1976 4.3 v-6. I have installed sunpro guages with the temp sender in the intake manifold. I just saw 220 on the guage and I can lay my hand on both the intake and the radiator. It is not the guage ,as two different guages have read the same. Is there another placement for the sender? Will it make a difference?
That is the common placement of the sender as it measures water temps coming OUT of the engine (the flow is in on the lower hose and out on the upper) Was it a spike at 220* until the thermostat fully opened or held constant 220* when you touched it? I would hazzard to guess if the thing is full of coolant and the temp gauge was reading 220 you would be very uncomfortable holding your hand to the thermostat housing.... Have someone with a non-contact pyrometer double check the surface temps to get a 'reality check' on them.
I like em to be in the head, if the stat sticks you still get a reading. The cheaper guages have the capillary sender, is yours electronic? if so, are you sure you have the right sender for the gauge? there is a dummy light sender and a gauge sender, each calibrated differently. or I could be lyling to you.
Also make sure the guage is grounded , I had one that the ground wire had broke on uner the dash and it read real high. Still moved from 0 though like normal and would shoot to 240 in 5 minutes. The engine wasn't even luke warm. Good to scare ya though.
For reference, 140 F is the borderline for thermal burns. You get pretty uncomfortable well before that.
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