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Old 08-13-2004, 05:20 AM
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Flex Fan cfm

Hi, I was wondering if anyone has a link or info on the cfm differences between flex fans. I have a 67 camaro with a 454. I just changed my whole cooling setup because I want to run a air conditioning. I bought a large condensor that I had to mount very close to the radiator. The ac is not hooked up yet but the engine would go to 230 degrees in 35 minutes idling. Once I removed the condensor the temp went to 185 degrees. I have a new 31" aluminum radiator, edelbrock water pump, march overdrive pulleys, high flow 160 thermostat, 18" large cup flex fan and stock shroud. What I want to do is build a bigger fan shroud to accept a 20" flex fan instead of my 18" if there is much difference in the cfm. I am hoping this will let me put a smaller condensor further from the radiator. and still get good cooling. I know I've seen some info on fan cfm before but I cant find it now.
Thanks Kevin

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Old 08-13-2004, 08:00 AM
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Get rid of the flex fan and go with a steel fan.
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Old 08-13-2004, 09:07 AM
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johnsongrass1, I just pulled the solid fan with a derale clutch off yesterday. I couldnt see any differerence in how long it took to heat up. Both took 35 minutes to get to 230 degrees before I pulled the condensor out.
Thanks Kevin
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Old 08-13-2004, 12:15 PM
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Could try running a couple of electrics. That would also free up some room and tension along the pulleys. I'd recommend dual depending on how big your rad is. Or try one as a pusher fan and the other as a puller.
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Old 08-13-2004, 01:33 PM
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Solid fan no clutch, how thick is the radiator?

RPM at idle?

What pulley ratio and arrangment?
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Old 08-13-2004, 02:16 PM
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I looked in my PAW catalog but didn't see a 20" listed, 18" was the biggest I saw. They have a really good break down on the specs for the electric fans but not much on the mechanical ones. As far as dia. vs CFM , diameter doesn't seem to be the deciding factor. The electrics a run around 2000-2200 rpms and the pitch of the blades controls Cfm but the more pitch/cfm the larger the Amp draw. The biggest Cfm single blade elecrtric is a Flex-A-Lite "black Majic" puller fan 2800cfm 13.9amp draw @ 13.5 volts. it comes with an adjustable thermostat and an A/C relay to turn the fan on when the A/C is on. PAW price $204.00. This should solve you hot at idle problem as mechanical fans don't pull as much at idle. They also list a Double that pulls from 3300-5000cfm 12-28 amp draw @13.5 volts but needs a 17"h x 32"w x 4.5"d mounting surface comes with the same hardware @ $400. The electrics will give you the air flow at idle/low rpms that you need with A/C and would be the best way to go as long as your electrical system can stand the amp draw and maintain a least 13-13.5 volts.
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Old 08-13-2004, 02:40 PM
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I dont know what the pulley ratio is but its the march pulley setup for high water pump and fan speed. I am trying to stay away from the big electric fans because of the high amperage draw and low dependability. I have a flexalite M150 in my shop that was on its second motor. The first one gave up the first season I had it on my race car. Not very many hours on it. Jegs is where I see the 20" flex fan. I noticed when the some electic fans go from 14" to 16" they pick up between 200 to 450 cfm. I figure going from a 18" to a 20" might be more.
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Old 08-13-2004, 02:56 PM
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GM makes a large solid high pitch steel fan that can't be beat for pulling air. Part number 405442. You will lose a couple HP for moving so much air but then so does putting on A/C.
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Old 08-13-2004, 03:00 PM
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How many rpms will the gm fan go and does it go on a clutch.
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Old 08-13-2004, 04:06 PM
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you just can't do better than good elec. fans.they as depenable as anything.i spent 20.00 on a dual 11" toyota fan and haven't looked back since.mounted on the inside of a 31x19 radiator i can light a lighter and hold it 3' in front of the radiator and it pulls on the flame.ands saves probably 8-10 h.p. to boot.come into the 21 centry.
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Old 08-13-2004, 04:17 PM
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Well if your using a flex fan get that thing as close to the Rad as possible(but not too close it may hit your Rad when it flexes) this requires a pretty thick spacer you can get out of Jegs fairly cheap.

But if you want my advice go with a clutch or electric fan, much safer and effective IMO
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Old 08-13-2004, 05:38 PM
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On the fan spacing flexalite recomends the fan be halfway in and out of the fan shroud. Guys, I think I have my cooling problem solved with the flex fan and moving the condensor. My question was wheather anyone has info on what different size flex fans cfm's are.
Thanks Kevin
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Old 08-17-2004, 06:10 AM
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Quote:
Originally posted by Full Throttle
How many rpms will the gm fan go and does it go on a clutch.
Sorry, didn't see the question earlier. THis part number is the same used by many late model dirt track racers who turn between 8 and 9 depending on track and engine set up. It is a solid fan and cannot be mounted to a clutch.
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