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I have been told that flex fans help with horse power.....and I have also been told that they do not help with anything....I am thinking about buying one for my chevy, but I dont want to waste the time and money if its not going to do any good......does anyone know the honest answer?
 

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I'm a fan of clutch fans.

On the main board I post on, the old hands unanimously trash on flex fans. Of course they would probably unanimously trash on Chebbies, but thats beside the point. :D

Seriously though, I would recommend a stock fan with a hydraulic clutch, aka 'clutch fan'. Commonly found on cars with a/c, the clutch makes it so the fan only turns at various RPM's as needed, thus being more efficient.

Flex fans just arent as efficient as advertised, and can even be dangerous, IMO.

For the record I prefer belt driven fans over electrical fans too, because if something electrical fails, you are screwed. As long as you have a fan belt, you are good to go with old school fan.. Also, a must in my book, make sure you have a fan shroud. Makes for MUCH better cooling and is a lot safer too.
 

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i agree with a-body totaly. go clutch fan, i had one and it helped on my power . flex fans are supposed to flatten out at high rpm to reduce drag. i would go with the clutch fan and like a-body said if you got a belt pulling it, you'll be just fine................adam
 

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Some Punk Kid
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Is it a daily driver? If it is i have to agree with A-body. If its a cruiser or a racer electric fans and water pumps are ideal for gaining all the horsepower possible. Special care must be taking with electric components. Corrosion and close proximity to high heat sources will make your electric components connections fail. Especially over here in Michigan. Wire connections, terminals, switches, relays all need to be taped up, sealed up and looked at every so often. So they require a little more maintenance than a belt drive fan/water pump. And typically the electric stuff cost more in almost all situations.
 

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A-BodyFan said:
On the main board I post on, the old hands unanimously trash on flex fans. Of course they would probably unanimously trash on Chebbies, but thats beside the point. :D

Seriously though, I would recommend a stock fan with a hydraulic clutch, aka 'clutch fan'. Commonly found on cars with a/c, the clutch makes it so the fan only turns at various RPM's as needed, thus being more efficient.

Flex fans just arent as efficient as advertised, and can even be dangerous, IMO.

For the record I prefer belt driven fans over electrical fans too, because if something electrical fails, you are screwed. As long as you have a fan belt, you are good to go with old school fan.. Also, a must in my book, make sure you have a fan shroud. Makes for MUCH better cooling and is a lot safer too.
there not hydraulic clutches, there is a heat sensative winding that will lock in when it's hot enough.
 

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personally I stay away from flex fans, I ran one years ago on an old stock car and during one race it threw a blade and sliced through my power steering lines just like a razor. If it flew apart while I had the hood open It could have done some serious damage to me or anyone else who happened to be close by.
I would go with a good clutch fan or electric myself.

Chris
 

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I need a bucket of arc sparks
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I have run flex fans for years and haven't had one problem, but that doesn't mean they don't have their issues. I have heard that at high rpm for extended periods of time that the fan blades flatten out and form a solid barrier against the air flow through the radiator. I don't run on roundy rounds, just a few blasts on the 1/4 every once and a while, so I don't have a problem with the fan flattening out. The real advantage with a flex fan is reduced weight on the water pump. This theoretically slows down wear on the water pump bearings. Clutch fans are better for moving air but they weigh a lot more and will wear out water pump bearings faster. This is where electric fans come in, they are light, don't wear out bearings and move sufficient air flow, but they can be expensive. A flex fan will cost less than the clutch fan or a electric but they can throw blades. If you buy one, periodically inspect it for cracks by the rivets that hold on the blades. If cracked, take it off and throw it away immediately.
 

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matt167 said:
there not hydraulic clutches, there is a heat sensative winding that will lock in when it's hot enough.
There ARE different clutch type fans

One is like the one you mentioned
Another (not sure if hydraulic is correct) will warm a silicone substance and engage---has no thermal spring on it.

Bryan
(six vehicles--4 electric fans)(electric on 79 Chev pu since 1990-no problems)
 

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OK, maybe my term 'hydraulic' may be improper useage here, but yes, there can be a viscous fluid within the clutch and/or a (typically) bi-metal thermostat in conjunction.

I guess perhaps the better terminology would be viscous fan clutch.
Here's my understanding of it: As the engine gets hotter, it needs more fan rev's to keep it cooler. The thermostat senses the heat, when the viscous fluid gets hotter, it gets thicker, and makes the fan turn faster.

Whatever you want to call it, or however it works, if you've got a daily driver, go for it! :thumbup:
 

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As seems to be the concensus here, a properly operating clutch fan is the ideal set-up for street use. Although many people use the aluminum flex fans without problems, a friend of mine has a blade imbedded in the ceiling of his garage to serve as a reminder that they can come apart with extended high rpm operation. I don't know about anyone else, but I get nervous around flex fans.

The only thing I don't care for in regards to the clutch fans is when your sitting in traffic, the engine is heating up and you cannot just rev the engine a bit to get more airflow.
 

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Flex fans are fine in some applications - a daily driver would be fine. When they flex, they are bending. When you bend something time after time, something will eventually break by low cycle fatigue - the old bend-a-paper-clip until it breaks trick but larger in scale.

Dave
 

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Another problem with flex fans in low speed driving. I put one on the 460 in my '32 pickup and almost immediately encountered problems in extended stop and go, low speed, traffic. In fact, at the Wisconsin Dells Car Show last year I overheated to the point I had to pull off the street and let the engine cool down for a while...and that had NEVER happened with that engine before. The next day I put my stock fan back on and have not had a lick of trouble since. I'd go with the majority opinion here and stay away from the flex...that is unless you want to buy mine.
 

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I recommend a stock type fan clutch and fan, if possible. Definitely shouded properly.

DeRale makes the best stainless steel flex fans. www.derale.com click on the pictures.

http://www.derale.com/heavy-duty-flex-fan.html

Not all flex fans are bad, (plastic sucks) ..... just as not ALL tires are bad just because Jim-Bob had a blowout or an out-of-round xxx brand tire.

Flex fans get a bad rap about flattening out or pulling excessive power from the engine. That is true when tested on an engine dyno or a chassis dyno when the car/engine is not moving.

Example: If the fan is pulling air through the radiator at 50 mph and the forward motion of the vehicle is such that the air naturally coming through the radiator is 50 mph (or more) then the fan load is ZERO. It is consuming ZERO power and NOT flexing.

Think about it.
 

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xntrik said:
I recommend a stock type fan clutch and fan, if possible. Definitely shouded properly.

DeRale makes the best stainless steel flex fans. www.derale.com click on the pictures.

http://www.derale.com/heavy-duty-flex-fan.html

Not all flex fans are bad, (plastic sucks) ..... just as not ALL tires are bad just because Jim-Bob had a blowout or an out-of-round xxx brand tire.

Flex fans get a bad rap about flattening out or pulling excessive power from the engine. That is true when tested on an engine dyno or a chassis dyno when the car/engine is not moving.

Example: If the fan is pulling air through the radiator at 50 mph and the forward motion of the vehicle is such that the air naturally coming through the radiator is 50 mph (or more) then the fan load is ZERO. It is consuming ZERO power and NOT flexing.

Think about it.
So, what you are saying basically is that a flex fan operating in an extremely narrow range where the rpm of the blades is moving air at the same volume and velocity as the incoming charge of air due to the movement of the vehicle consumes no energy?

I agree with you, but what about the other 99.999999999% of the time?
 

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Bryan59EC said:
There ARE different clutch type fans

One is like the one you mentioned
Another (not sure if hydraulic is correct) will warm a silicone substance and engage---has no thermal spring on it.

Bryan
(six vehicles--4 electric fans)(electric on 79 Chev pu since 1990-no problems)
yes there is a clutch type that uses a silicone compound in it. it works by staying in 1 compartment until it's warm, then it seeps into another and locks up the clutch, not 100% shure that's how it works, I'd have to look back thru my auto class notes from last year to be shure.
 

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I personally think the flex fans suck.
I used one in my NA Gremlin and the temp was reaching as hi as 200-220 degrees cruising and higher at stops.
I put an old 7 blade metal fan on and it never got over 180 after that.
The 5 xtra horses you get using those alluminum time bombs arent worth the hassle. HG
 

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I do not like the flex fans either.......5 extra horses.......I really don't believe that...I would have to see it on a dyno.
 

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I never had a viscous drive apart before, so I'm not real sure how they work, but what I think is that they drive the fan blades like a torque converter does up to the point that resistance is met by the speed of the fan. Then they just slip. You don't need a fan above 35 miles per hour anyway. That's how you tell if you are not moving enough air through the radiator. If you are overheating at speeds over 35, then you need to make some holes for the air to get out of the engine compartment.
 

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Henry Highrise said:
I do not like the flex fans either.......5 extra horses.......I really don't believe that...I would have to see it on a dyno.
It was just a number i picked. hg
 

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sitis nam accelero
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I currently have a flex fan, have no problems but I am looking for better cooling and as the flex fan flattens out at high RPMs they become useless. I'm deciding on whether or not to go with clutch or electric fan. They are very light, put less stress on the pump and take less power to use, but you are losing cooling potential for higher RPMs unless you are only operating a vehicle in the low-mid range. Even though you are getting decent air flow pushing through the radiator at high speeds, it's always good to have something on the other side pulling. Same goes for the other way around, especially if you are doing some low speed high revs, where you aren't getting much air flow in the front...
 
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