ORIGINAL:Also, I've never heard of an engine that ran 'well' at temperatures over 300 F unless it had an air leak. Most engines run best at around 230-250. Sometimes the ambient conditions will dictate temps even higher. But if you experience temps over 300 without a lean bog, I'd bet you have an air leak.
Not necessarily, My O.S. CV ran well over 300F for a few gallons without any loss of performance at all. It did not have any leaks and ran 110% reliable all the time , I added a hyper head and that reduced the operating temperature down to 250-260.
Any experienced engine guru will tell you to tune the engine by performance, not by temperature. And if that means over 300F, so be it, it does not hurt the engine.
As I was saying about my 412 temp, I never run engines that hot, this was just an old engine that i was playing around with.