Originally Posted by steco1958
Forgive my ignorance, I'm not a mechanic, what is the self tapper keeping open ?
It's the thermostat housing and someone on here correct me if I'm wrong as I too am not a mechanic but it appears that the owner used the screw to prevent the thermo from being stuck open which makes the engine run too cool which causes the engine to run too rich which really reduces performance efficiency.
It's normally not a big deal to replace the thermostat with a thermostat kit which the seller opted to not do. You now have to wonder if the rest of the engine has been abused and if it has experienced overheating.