No time now a garrage / cave to move , but .
Mini A series engines , there was a competition part called a "blanking plate" , this was actually a tube to make the water flow properly inside the iron head casting . The biggie with a Mini racer was to take water from the heater take off I think at the other end of the head and run it through an auxilliary radiator ie a spare heater core in the nose .
Drilling thermostat plates makes engines warm up slowly , the only reason manufacturers have holes and jiggler valves is to bleed air from the system if the coolant is drained and refilled .
I think the ONLY reason to drill them is if your engine has a brown head gasket and is pressurising the cooling system ie forcing gasses in . Where gas goes water isnt and cannot cool the head and block jackets leading to warping and cracking . A Charade I once had had wire threaded underneath the thermostat valve keepnig it at least partially open and I had to run it with the cap unlatched to leat the air constantly out of the system .
This is full damage control to nurse an ailing engine whilst trying not to kill it .
Lots of Coxy wisdom here , cheers A .
