My first time to post so please excuse me if I do something stupid. I have a 1966 Mustang. 289 engine. I recently replaced radiator and fan with a three core aluminum radiator and electric fan. Electric fan is set to approximately 180deg F. During the upgrade I also replaced the thermostat (also 180deg F). However, the temperature keeps rising past 180degs. Any suggestions on what can be causing my overheating problems? Anything else I can check? Electric fan is turning on at approximately 180deg. I used a heat gun to measure.