I'll get the "dumb" comment over with first:----Be sure that you topped off the cooling system again after having run the engine long enough to make sure that all the air has been bled from the system. I had the same problem with my 440 until I installed a fan shroud after a previous owner had removed it for some reason. Now have no overheat problems even though here in Alaska summertime temps can get into the high 80s and lower 90s. I don't remember where I got the information on how to test a fan clutch but I used the method and it really did work, so I'll pass it on here for anyone who doesn't already know;---Do the test starting with a cold engine. With the engine at idle take a rolled up newspaper and hold it at an angle so that the tip of the paper makes contact with the spinning fan blades as the blades are spinning AWAY from the tip of the newspaper. Apply a little pressure against the blades and if you can stop the blades on a cold engine then the fan clutch is no good. With the engine at operating temperature you should be easily able to stop the fan. I was a little hesitant to do this kind of test but if it is what $100 an hour mechanics do then it must be ok? From what I've been told is that you can't really tell accurately if the clutch is good by feeling "spin resistance" while the engine is cold and stopped, because it is the fluid inside the clutch that "grabs" the fan blade mechanism through centrifical action. Simply put the colder the fluid is the more it "grabs" and the hotter it is the less it "grabs". It's a little noisy but it works and is simple to do. Just don't donate a finger or two doing it!
