Hot 170

Suspect a plugged up radiator or perhaps it's cap is not holding pressure, check cap, and have it boiled out if cap is good. Also flush out block and head, remove block drain lower passenger's side of block below #5 park plug; you may have to bust through some slag with a screw driver or such after removing plug to get water to flow.

Also inspect water pump, its impeller may have failed from corrosion and no longer can pump.

Put a 180 degree thermostat back in with 50/50 mix of water and anti freeze.