To get a pretty good indication of the accuracy of the dash gauge, try using a small camp stove under the hood, maybe setting it on the intake manifold, to boil a small pan of water and put the sensor bulb into the boiling water. At least that will give you a reference for the "no pressure" boiling point the gauge is indicating.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!