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drolston · 10-21-2019, 09:57 AM

I can't tell you the CFM, but I can tell you that whatever it is, it is not enough at idle on a hot day. Two problems: The fan turns at crank speed which is substantially lower than belt driven fans, because belt driven fans get "geared up" by having a smaller pulley than the crank pulley that drives them. The other problem is that the crank mounted fans are low and not centered on the radiator. Some cooling is lost because more air is sucked up from under the radiator, rather than through the radiator.

10-21-2019, 09:57 AM	#2
drolston Senior Member Join Date: Jun 2014 Location: Williamsburg, VA Posts: 1,627	Re: factory fan cfm I can't tell you the CFM, but I can tell you that whatever it is, it is not enough at idle on a hot day. Two problems: The fan turns at crank speed which is substantially lower than belt driven fans, because belt driven fans get "geared up" by having a smaller pulley than the crank pulley that drives them. The other problem is that the crank mounted fans are low and not centered on the radiator. Some cooling is lost because more air is sucked up from under the radiator, rather than through the radiator.