Indy heads single water crossover /single plane manifold.

Texas Red said

I had high quality 185 degree thermostat in the car but removed it today...

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Texas Red said

Engine started great at 8 degrees and Car ran flawlessly to town and back at 170 degrees.....edging up at red light and small city driving......to fuel up the beast. After eating up $75 dollars of super unleaded the car ran 170 all the way back home. (More on this later)

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What makes the thermostat high quality? What is the diameter of the opening section of the thermostat? If you removed the 'stat and the hot problem went away, it is a flow issue. The real high performance thermostats are 1 7/16" at the opening port. The old factory thermostats from '67 - #2128994 or a similar new one as below:

EMP/Stewart Components 301 EMP Stewart High Performance Thermostats | Summit Racing