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-   -   Flex Fans (http://www.moparchat.com/forums/showthread.php?t=119249)

mikeynags 05-02-2010 04:16 PM

Flex Fans
 
What do you guys think of them? Are they good or should I stay away?

aarracer 05-02-2010 11:08 PM

I'll vote for the "stay away" side.

cudabob496 05-03-2010 12:55 AM

Well, they're lightweight, and they flatten out at high rpm to reduce power losses. I here they are noisy.

JVMopar 05-03-2010 09:49 AM

I've read that a clutched 7 blade takes less HP than a flex fan.

And when they flatten out they actually block airflow.

Just what I've read, I've never used one. But Cuda's right they are NOISY

cudabob496 05-03-2010 06:41 PM

I agree, the viscous fan assembly from MOPAR for about $150 is the way to go. However, if you have an aluminum radiator, and a vented engine compartment, then you can get by on a cheapy electric fan from Summit, as I have been doing for the last 5 years. As long as my 496 Cuda is moving, I rarely have to turn the fan on! Make sure you have a fan shroud, but not one that blocks off all the air coming through the radiator!

cudabob496 05-03-2010 06:42 PM

Quote:

Originally Posted by JVMopar (Post 799738)
I've read that a clutched 7 blade takes less HP than a flex fan.

And when they flatten out they actually block airflow.

Just what I've read, I've never used one. But Cuda's right they are NOISY

I would imagine the light weight is a horsepower saver?

madmax4073 05-03-2010 07:14 PM

I seen a '79 Camaro that had a flex fan that came apart at about 5000 rpm. It did some pretty good damage.

Tarrbabe 05-03-2010 07:57 PM

I saw one that came apart at the drag strip...
 
The owner was really pissed. Did you know that a fan shroud serves well a a funnel toward the radiator?:devil:

Just thinking out loud.

LD 05-03-2010 08:05 PM

I had one
 
set about 1" into the shroud on a '76 Dodge pickup with a 440 that flexed a bit too far and ended up going through the radiator. Cost me about nearly 500 to fix all the damage it caused. I have never ran another one because of it.

Dart 360 05-04-2010 12:30 AM

I have a 318 with a flex fan, the only reason its on as the car came with it, I have seen the damage they cause. I have bought the factory viscos fan, consumes less power and much safer, doesn't restrict air flow when disconnected.

Rich Kinsley 05-04-2010 12:39 AM

The clutch fans always get the vote it seems. But to me they seem so heavy and I had one on that I do believe was out of balance and ate up my water pump bushing. A good shroud and clutch fan probably are a good deal but I've run the flex fans most of the time with no problems. Mine now is a $47 Summit aluminum fan. Very light.

cudabob496 05-04-2010 02:29 AM

Ya, my engine can rev to 6500, and a flex fan at that engine rpm could easily
become a grenade it seems!

cudabob496 05-04-2010 02:31 AM

Quote:

Originally Posted by Rich Kinsley (Post 799796)
The clutch fans always get the vote it seems. But to me they seem so heavy and I had one on that I do believe was out of balance and ate up my water pump bushing. A good shroud and clutch fan probably are a good deal but I've run the flex fans most of the time with no problems. Mine now is a $47 Summit aluminum fan. Very light.

They are heavy. Thats why I went with the aluminum radiator and cheapy electric fan.

JVMopar 05-04-2010 10:30 AM

Yes the fan and clutch are heavy, but that's why there is a clutch. When the clutch releases that weight is just sitting there not rotating eating up HP.

cudabob496 05-04-2010 12:10 PM

Quote:

Originally Posted by JVMopar (Post 799815)
Yes the fan and clutch are heavy, but that's why there is a clutch. When the clutch releases that weight is just sitting there not rotating eating up HP.

If an engine is warmed up, at what rpm does it release? I've heard around 3500?

rampage_82 05-04-2010 01:40 PM

It really depends on what style of clutch fan you are dealing with. The cheap ones just hold to a certain rpm, while the thermostatically controlled ones just kick in above a certain temperature... I prefer the latter....

JVMopar 05-04-2010 03:24 PM

I also use the thermostatic heavy duty ones on my trucks. Cold they stay on for the first 1/2 mile or so. Sounds just like a flex fan. After that they don't ever sound like they are engauged. Even cruising around at 2000 rpm you don't hear them.

Of course an electric fan would use the least HP, but may not always keep it cool. I want to put one in my '90 W150 see if I can break 20mpg with it. Got 18.5 on the last long trip.

cudabob496 05-04-2010 05:47 PM

Quote:

Originally Posted by rampage_82 (Post 799824)
It really depends on what style of clutch fan you are dealing with. The cheap ones just hold to a certain rpm, while the thermostatically controlled ones just kick in above a certain temperature... I prefer the latter....


Well, I heard the Mopar viscous unit will not engage until things warm up, but I also heard that even when car is warmed up, the viscous unit will disengage above a certain engine rpm to save hp, because the car is assumed to be moving fast enough, while at the high rpm. Thats what I like about electric fans; If you're getting ready to boogey, just turn it off and forget about it until after the run.

djswwg 05-04-2010 10:16 PM

i saw one grenade on a 350 chev, and the car was parked! the owner was tuning the engine and gave a few shots on the carb while leaning over the fender. a couple blades came off, took out the shroud and hood and cut buddies face about 1/2" from his eye. no problem a bandage couldn't fix but if it had hit his eye he'd have been in very serious trouble. you couldn't pay me to use a flex fan-matter of fact i think they should be made illegal because they are so dangerous. and no i don't care how many guys "use them without any problem". ...............djs

pcrmike 05-04-2010 11:55 PM

Wow. I used one at 6K plus on my old crew cab. I never knew they were such a risk. Mine was prolly 20 years old. Never had an issue, but still...

cudabob496 05-05-2010 12:21 AM

Quote:

Originally Posted by djswwg (Post 799855)
i saw one grenade on a 350 chev, and the car was parked! the owner was tuning the engine and gave a few shots on the carb while leaning over the fender. a couple blades came off, took out the shroud and hood and cut buddies face about 1/2" from his eye. no problem a bandage couldn't fix but if it had hit his eye he'd have been in very serious trouble. you couldn't pay me to use a flex fan-matter of fact i think they should be made illegal because they are so dangerous. and no i don't care how many guys "use them without any problem". ...............djs

good reason to have a shroud that covers the entire fan

aarracer 05-05-2010 12:18 PM

Mid 70's 318 AC cars had 7 blade aluminum fans that can be trimmed back to fit the shroud.


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