O.k. I'll give this a shot tink. Coolant does go through the carb but only in through the auto choke mechanism. Coolant also goes through the base of the carb in a chamber under the plenum in the manifold. If it runs dry it won't damage the carb. Please say you didn't fill the radiator while the engine was hot - this would be enough to split the head (even if it showed it didn't bake on the temp gauge). So you don't have any cross contamination of fluids in the engine which is a good sign. Could be that the carb happened to choose a time to quit completely when you had a cooling system fail. If the choke has decided to stay shut it will ruin the way the engine runs (you'll get all the symptoms you're experiencing - running way rich, no power on throttle etc) Pull the air filter box off, start it when it's dead cold and watch the auto choke butterfly. If it doesn't move or moves very little in the normal time it would take for the engine to warm up then you have found the culprit.