Over heating 66 Dart

How can my 67 dart, 273, stock 7 blade fan, no shroud, blade is about 2 inches from the stock radiator idle all day with out ovetheating.

It must be pully diameters (IIRC are about the same), and fan pitch / diameter.
Colorado. Not the south or southwest. Whats the hottest it gets there, 85?

Jake