Cleaning water jackets 225

Do you have the PN for the new sensor? Some of the listings are incorrect. Do you have an ohmmeter? If so, you can take the wire off the sensor, warm the car up to hot, and measure the resistance through the sensor and list it; I can probably tell you if it is waaay off. And, I would now take the '69 sensor and put that in and see what the gauge shows; in that waym you are comparing both engines with the same sensor/gauge/limiter combo.

But using the temp gun or the thermometer is really what you need to do to see what the temp really is. We can mess around with sensors but the limiter and gauge are part of that equation, and you don't realy know precisely what the temp is with ths stock system.

The core plug blowing out hot is inconclusive, it just may not have been put in well. They rarely ever blow from hot coolant.