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I kept looking around and finally found an ultra thin electric fan that will fit behind my raduator. Its a Flexalite model #120. It comes in at only 2 1/4 inches thick and pulls 1250 cfm's. Thats the most draw for any of the ultra thin fans that I have found.

Considering that my car is not on the street any more and the most time I will have to idle it is tweaking the carb or timing or sitting in the pits for a few minutes waiting to run I think it should be fine(he said, LOL).

According to the fan companies I am supposed to need almost double the cfm rating of that fan to keep my motor cool. I remember other vehicles I've driven with electric fans(my Z 28 for example) and the fan hardly ever even came on and that was usually when I was sitting at idle for a long time and it was fairly warm outside.

I don't understand where these cfm requirements numbers come from. I know my old rigid blade fan didn't pull anything close to 1250 cfms at idle. However, with that fan my temp would creep up if I had to idle very long. I went to that little electric fan that I was using which came off a 4 cylinder car. It blew plenty enough to keep my motor cool even when I was street cruising around at low rpms in 110 degree weather this last summer.

It seems to me like these fan cfm numbers need to be elaborated on. Somebody needs to come up with a more accurate cfm calculator so that people like me about to buy a new electric fan will be able to have a better guestimate of how much cooling I need before I go buy something that may not work.

For example, with or without AC seems like would have a big effect on it but how many extra cfm's does that require? I would guess that whether you run a thermostat or not and what the thermostat rating is would affect it. I run a restrictor in my car and no thermostat. Cars that have slanted radiators boxed up in the nose would not have much in the way of any ambient air which seems like would make it run a little hotter. Of course my radiator is more square and thicker compared to most newer cars that have thin wide radiators. Surely somebody out there has done this sort of testing and analysis but I've never seen anything in the way of a cooling system analyzer or calculator.




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You're right, the CFM #'s are as varied as the mfg's. The best units out there (IMHO) is the electric fans from the Mark VIII and Police package mustangs/LTD's. Each are rated at 10,000 CFM (if I remember correectly) and are very inexpensive compared to "Aftermarket" units (used about $50, new $150). Another option is to place a portable fan (commercial type) in front of the car while it's sitting in addition to the small fan you're describing.

Jeff
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I don't have an answer for you Hottarod, but I have to agree that the flow ratings can be deceptive. Some partners were doing the fan for a race car project of ours, they sourced an aftermarket fan and it turned out to be inadequate. It was a Flex-A-Lite or similar with a flat motor. The numbers looked good but in practice it couldn't compare to one sourced from a water-cooled VW. I think the shrouding has alot to do with it, the shroud changes output quite a bit via efficiency. Do you need a thin unit because of space constraints or because you want it to hide away?

Ollie
 

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Check out the SPAL fan I use on my website. It pulls about 2800 cfm, being a dual fan it is very thin in the center where the waterpump pulley is and manages to fit in ok with my 351C and 4-row radiator, A/C compressor, power steering etc, it also has a well designed shroud. I couldn't praise it more. Also check out SPAL's website or one of the online shops for their range of fans, this page has the specs on the one I installed (2.6" deep in the middle). http://www.carolinarodshop.com/11dual.htm

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