lifendet said:
if you leave it open, coolant will just flow right out of the block and say bye-bye to your engine. new information has been found that you cannot plug the hole or weld it shut. the coolant flowing out of the head helps heat up the thermostat so it can open. people now are tap it so they can fabricate a hose connection to allow the fliud to flow back down to the thermostat. i just said the hell with that crap and am usning a type-s A2 head. much easier to work with. and i got it for free. good luck