Differences in Factory Fans

[holanae]

Asked one of our fellow members if he had any factory radiator fans with the thermal clutch.  He said he has four to choose from.  They all measure right under 19 inches which I think is correct for my oem fan shroud, but he said he has two different blade widths.  Does anybody know the difference?  Maybe late 60 vs early 70 versions?  Not really concerned about date specific as much as I am about fitment.

[John_Kunkel]

The diameter will be the critical dimension for clearance to the shroud or surrounding parts. I believe there are more than two blade widths over the years and it's not only the blade width but also the blade pitch that affects ir flow.

Wide blades with a steeper pitch will move more air but they also take more power to drive and are noisier. I once had a 20" 7-blade cop car fan that felt like 40 mph on a Harley when standing behind it and it sounded like a helicopter flying over.