I don't know if it is possible that someone replaced the crank fan pulley with one with a larger diameter, but I have had a hard time finding a fan belt that is long enough to work. The Gates TR26366 that most sites sell (and the other manufacturers parts) are too short. With some work (pressing the fan down and flexing the shroud) I can get it on, but when I tighten it, it still rubs the fan shroud.

According to most of the auto parts books, there isn't a longer belt in this specific width. Not having a choice, I went to a more narrow belt (TR24365), but I don't want to try to solve a heating problem necessarily by spinning the fan faster. What was left of the old belt (the rats removed a section) showed it had been running in the bottom of the pulleys. By using a more narrow belt, mine will likely eventually do it as well, and just slip causing problems also.

Does anyone know the diameter of the proper crank fan pulley?

1949 Ford F3 with the 239 engine with wide pullies on the waterpump/gen.

 

The Ford parts book lists the 6312 pulley used from 1949-53. I measured three stock Flatties of that era and the pulley measures just shy of 5.5 inches O.D.

 

Thanks McKay356 for the confirmation! That is what mine measures as well. I guess I'll just stick with the TR24365 belt.