Clutch fan vs. Flex fan
Thread Starter
Safety Car
Joined: Jun 2001
Posts: 4,004
Likes: 2
From: Severna Park Md
Clutch fan vs. Flex fan
ok two questions pitting these two agains one another. Factory 7 blade clutch fan vs 7 blade flex fan.
1. which one pulls more air?
2. which one robs less power?
1. which one pulls more air?
2. which one robs less power?
Burning Brakes
Joined: May 2000
Posts: 765
Likes: 0
From: Canton GA
Re: Clutch fan vs. Flex fan (73-454)
I have one you can have for free, if you want to pay shipping. BUT I put it on my car, and it ran 20 degrees hotter than with the old clutch :mad:. May be lighter...but this is one time stock is better! If I were looking at replacing a fan again...it would be with electric ones. Just my $.02.
Race Director
Joined: Mar 2001
Posts: 11,322
Likes: 1
From: Living in the Hartland
Re: Clutch fan vs. Flex fan (Jvette73)
If you got feed back, post which fan you are using (plastic, steel, aluminum, etc) then we can get a better idea of which ones people like or don't. I have a aluminum flex and it works well. And looks better too. But I can't say for sure if it works better than clutch assembly.
Melting Slicks
Joined: Jun 2001
Posts: 2,340
Likes: 2
From: Moro IL
Re: Clutch fan vs. Flex fan (Jvette73)
A magazine about a year back, I can't remember which one did some comparison tests as far as power drain, flex fans were the worst, and the clutch fans robbed some but not near as much as the flex and of course the electric was the best from this standpoint. I have a tendency to believe that the flex fans cool better at idle then clutch fans since they don't have any slip, but of course a good electric can do even better since it's speed is constant while clutch and flex are engine speed dependent. In my oppinion there is really only two options, clutch or electric.
:cheers:
Pat Kunz
:cheers:
Pat Kunz
Pro
Joined: Apr 2001
Posts: 591
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From: Morinville Alberta
Re: Clutch fan vs. Flex fan (Fevre)
If you got feed back, post which fan you are using (plastic, steel, aluminum, etc) then we can get a better idea of which ones people like or don't. I have a aluminum flex and it works well. And looks better too. But I can't say for sure if it works better than clutch assembly.
Me to I went with a flex fan because I had one from a previous car and my vetts clutch was messed up so the flex was an improvment.
Race Director
Joined: Jan 2000
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From: Corsicana, Tx
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Re: Clutch fan vs. Flex fan (Aaron76)
I have been using the same 7 blade stainless flex fan for 20+ years with no problems. Mainly because I have it and it always works.
Clutch fans are great but make sure you get a quality clutch. Many cheap ones slip like crazy. A thermo controlled one is best, but naturally it uses slightly more Hp because it locks in better.
Just to give some facts though... I did a back to back comparison on my car on the chassis dyno. With and without fan. Difference was in the 3 rwhp range at 7000+rpm. Not enough to get excited about considering the simplicity of the setup.
I have also tried back to back runs at the track doing the same test (with the old 427) and could see no measurable improvement.
Use whatever will cool your car. The old fiberglass ones are the ones that got the bad reputation going for them.
Jim
Clutch fans are great but make sure you get a quality clutch. Many cheap ones slip like crazy. A thermo controlled one is best, but naturally it uses slightly more Hp because it locks in better.
Just to give some facts though... I did a back to back comparison on my car on the chassis dyno. With and without fan. Difference was in the 3 rwhp range at 7000+rpm. Not enough to get excited about considering the simplicity of the setup.
I have also tried back to back runs at the track doing the same test (with the old 427) and could see no measurable improvement.
Use whatever will cool your car. The old fiberglass ones are the ones that got the bad reputation going for them.
Jim
Burning Brakes
Joined: May 2000
Posts: 958
Likes: 0
From: Brisbane, Australia 1985 Coupe
Re: Clutch fan vs. Flex fan (73 LS-4)
I have a tendency to believe that the flex fans cool better at idle then clutch fans since they don't have any slip, but of course a good electric can do even better ........
:cheers:
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Thread Starter
Safety Car
Joined: Jun 2001
Posts: 4,004
Likes: 2
From: Severna Park Md
Re: Clutch fan vs. Flex fan (Jvette73)
Ok, heres the story. I had the original clutch fan and it worked fine. I guess I assumed that since the flex fan was lighter it would rob less power so I put one on. Later I added an electric fan in combo with the flex fan. Combined, the two worked very well in cooling and it helped the a/c work better. Last fall before going to the track I removed the flex fan and went with the electric alone. It did a fully sufficient job throughout the fall, winter. Now that we have had the first 90+ degree day here in Md, I noticed the temp creeping higher. So when I got home I left the car sit and run with the hood closed for a test. Before too long the temp creeped up beyond 210. Max cooling is always my priority so I have decided to go back to the combo of both for the summer. I still have the factory clutch fan and the aluminum flex fan. One of them will be put back on in conjunction with the electric. The question is, which one will it be? Thanks for the responses. Im so wishy woshy sometimes and it helps to have input from others. :D
Race Director
Joined: Mar 2001
Posts: 11,322
Likes: 1
From: Living in the Hartland
Re: Clutch fan vs. Flex fan (Jvette73)
I didn't mention that I have a electric fan also. I tried it as a pusher (in front of the radiator) but found it worked better if I use it as a puller. I have it intalled with a switch so I can manual turn it on and off. I tried an automatic electrical thermastatic switch but it didn't work as well as I would like. Now I can turn the electical one on and off when I want to. One reason I like have the flex flan is that moves air around the engine which helps dissipate heat from the exhaust manifolds and bring cooler air to the carb.
Racer
Joined: Mar 2002
Posts: 369
Likes: 1
From: Nowhere
Re: Clutch fan vs. Flex fan (Jvette73)
My clutch went out on my fan as well, and installed a Stainless Flex Fan. I did notice a vast difference in cooling and wind flow. But I also noticed that it has a constant howling noise at certain RPM's, and this is normal due to the fan blades.
But my main concern was living in Rural Oklahoma, we have vast amounts of insects and grasshoppers around during the summer months. I noticed with the flex fan, it sucks up everything in it's path and clogs the radiator. :mad
I did have custom screens made for the grille and radiator to fit on the inside, and it did remedy the clogging. It just took time to pull the dead insects and grasshoppers off the screens.
So, I just went ahead and splurged for the nicer clutch, and put the factory fan back on. :rolleyes:
But my main concern was living in Rural Oklahoma, we have vast amounts of insects and grasshoppers around during the summer months. I noticed with the flex fan, it sucks up everything in it's path and clogs the radiator. :mad
I did have custom screens made for the grille and radiator to fit on the inside, and it did remedy the clogging. It just took time to pull the dead insects and grasshoppers off the screens.
So, I just went ahead and splurged for the nicer clutch, and put the factory fan back on. :rolleyes:
Melting Slicks
Joined: Apr 1999
Posts: 3,264
Likes: 3
From: Toms River NJ
Re: Clutch fan vs. Flex fan (kgraumann)
My clutch also went bad over last winter. I tried o find the right replacement clutch, but turned out that my water pump, clutch, and clutch fan were all off of another car. Had different pilot hole, bolt pattern was different, etc. So I couldnt find the correct clutch alone. So it was cheaper to get a flex fan than a clutch and the correct clutch. It seems to run a little bit warmer now that its getting hotter out. At idle for 10+ mins itt runs ~165-170, and on the highway at ~75-80 mph, it runs ~185-190. It fluctuates alot on the highway cause i dont have a front spoiler or air dam. but the flex fan works great IMO, and definitely looks much better than anything else.
However, as soon as I get enough money saved this summer, I will be going with a Spal daul setup :cheers:
However, as soon as I get enough money saved this summer, I will be going with a Spal daul setup :cheers:
Drifting
Joined: Jan 2002
Posts: 1,645
Likes: 11
From: Schaumburg IL
Re: Clutch fan vs. Flex fan (Jvette73)
I run a BB in a 73. The factory 7 blade and clutch work fine until the temps move into the 80's. Then the BB and compartment get hot. In the summer I run 90/10% distilled water, 2 bottles of water wetter and put on a 17" stainless flex fan with a 180 thermostat. This keeps it around 190-200. The flex fan works very well for summer driving. This has been the only solution for cooling that I have found and I have tried the carb jets, fans, timing, etc.
Race Director
Joined: Apr 1999
Posts: 15,154
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From: NM
Re: Clutch fan vs. Flex fan (Jvette73)
This is all hear say, but, a flex fan flattens out at higher rpm, thus any power saving, but this flat fan can act as a block at highway speeds (kind of like running a round disk as a fan) and stop air flow at the back of the shroud thus building high pressure inside the shroud and keeping air out of the radiator. Like I said, hear say, but something to consider.
tom...
[Modified by Tom73, 12:39 PM 4/17/2002]
tom...
[Modified by Tom73, 12:39 PM 4/17/2002]
Moderator
Joined: Jun 1999
Posts: 7,117
Likes: 51
From: Dove Mountain Arizona
Re: Clutch fan vs. Flex fan (Jvette73)
Got the 7 blade stainless flex fan on mine with an electric puller in conjunction. Elec. fan is 'switched' so I can use it in traffic. No overheat probs, no loud noise from the fan. Seems fine to me.
Melting Slicks
Joined: Mar 2000
Posts: 3,206
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From: WANTED: '68 rear valance with b/u light assemblies IM, e-mail, or PM me here. Thanks!
Re: Clutch fan vs. Flex fan (Jvette73)
I tried both on my ’64 S/S Dodge (Around 650 HP) and I didn’t notice any difference.
Pro
Joined: Apr 2001
Posts: 591
Likes: 0
From: Morinville Alberta
Re: Clutch fan vs. Flex fan (Tom73)
This is all hear say, but, a flex fan flattens out at higher rpm, thus any power saving, but this flat fan can act as a block at highway speeds (kind of like running a round disk as a fan) and stop air flow at the back of the shroud thus building high pressure inside the shroud and keeping air out of the radiator. Like I said, hear say, but something to consider.
tom...
[Modified by Tom73, 12:39 PM 4/17/2002]
tom...
[Modified by Tom73, 12:39 PM 4/17/2002]
The reason it flattens out is because with more rpm, more air is pushed until the blade tips reach the speed of sound (then the fan becomes inefficeint). When more air is pushed there is more stress created and the baldes bieng the weakest link flatten out as a result, but because the rpm of the fan is higher there is less of a pitch (blade angle) required to pass the same air mass as before with low RPM and a more pitch.
So as you see you will never create a high pressure in front of the fan.
I hope this helps
Burning Brakes
Joined: Jan 2001
Posts: 1,004
Likes: 16
From: Gainesville, Florida
Re: Clutch fan vs. Flex fan (Aaron76)
There was a test of all of the different fan configurations (including no fan as a baseline) in one of the car magazines recently. Aside from no fan, a stock steel fan with a clutch produced the most peak and overall power. Not sure if it was a centrifigal or thermostatic clutch. If it was centrifigal, it makes sense, at higher RPMs, the fan becomes undriven when HP is priority and cooling is not. At cruise or low RPM, it is driven providing air when its needed most and HP is needed least.
I'll look for the article and post if I find it.
Mark
I'll look for the article and post if I find it.
Mark
