Regardless of the possible merits of running at 220 instead of 180, if the cooling system is working properly the temp should be limited only by the thermostat. If you have a properly working 180F stat and the temp gets much higher than that, there is something wrong because the system can't reject enough heat to the air to get the temp back down to the stat opening point. Radiator too small or clogged, insufficient airflow (rarely a problem at speeds over 25 mph), water pump too slow, lower hose collapsing, etc. Let us know what exactly is going on, and when...