Cooling Fan CFM Rating

[focodave]

Does anyone know what the factory CFM rating is for the engine cooling fan on a 1980 fuel-injected Spider2000?

[spider2081]

Not sure where one would find the CFM out. I replaced the bearing in one and was bench testing it with the fan blade off the motor. I was surprised it drew very little current. So after I put the blades on the motor I rechecked it. At 14 volts the fan drew a little over 10 amps. Its a pretty powerful fan. I know people are putting after market fans on their cars. Doing some reading in hot rod chat rooms there is a little chatters about noticing with the higher output fans more of the radiator is blocked than what the original fan blocked. This blockage of air flow causes the replacement fan to run at higher driving speeds than the original fan. They feel the physical size of the higher output fan and shroud reduces the natural airflow through the radiator. I don't think that is a problem but it is something to think about.

[RRoller123]

Great observation! I commonly see the entire back of radiators (usually on tri-5 Chevys) blocked off by a dual electric fan setup with a shroud that covers the entire back of the radiator. So there is almost no natural flow through the radiator! The setup obviously works, since these guys drive their cars all over the place to these shows, but I expect, from a duty cycle standpoint, that the fans must run a lot more than they would if there were more natural, free air flow through the radiator.