I would like to install a mechanical water temp guage on my 70 Duster with a 1966 slant 6 225 engine. Can anyone tell me if the drain plug port on the passenger side of the engine is deep enough to accept a mechanical water temp probe? Also, does anyone have the size of the plug, so I can determine if the adapter for the mechanical gauge will work?
Thanks

In-coming coolant, in the lower block runs cooler then the coolant in the cylinder head.
Based on that, it is better to install your aftermarket temp gauge sender, in the thermostat cover.
DD

You can TAP the original temp sensor spot and put in a Mechanical Gauge sensor there. I am also going to do what DOC said, and wire in the original gauge there, to see if and when my thermostat opens!

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1964 Dart GT