How much HP is a flex fan going to rob? I know it is hard to tell for sure, but maybe how much loss compared to a clutch setup?
Thanks
Brady

I have the flex fan on my 454 with a 2 inch spacer and i love it drives around 190 all day as for Power, i didnt notice really any differnece

The single electric fan that came with the 305 TBI engine is not cutting it. Its motors fried and instead of spending $30 for another I think I am going to go flex fan with a 2" spacer. Thanks for the response.
Brady

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1992 Camaro RS - 355 and 3.73s (http://www.thirdgen.org/rides/index.tgo?action=view&rideid=8390)

Click here for pictures and some videos. (http://briefcase.yahoo.com/brodyscamaro)

Please do not buy just any flex fan. Most flex fans are junk!

Try going to www.derale.com (http://www.derale.com) and click on fans that look like this. This is a new fangled flex that do not shed their blades and afford the most airflow at low speeds and idle. I am using one on a 400hp+ Camaro ragtop with air here in Atlanta with no problem.

http://www.derale.com/img/ChromeHDFlexFan.jpg

ps...if you buy a quality electric fan such as a Spal or Derale, they will outperform any mechanical fan at idle and slow cruise.

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Steve "Jack'stands" Jack
Tech forum at www.inccn.net/techforum.htm (http://www.inccn.net/techforum.htm)

Thanks, is there any specific reason I should get a Derale over, say a, Perma-Cool one? They are similiar in price so if the Derale is better then there is no reason not to get the better one. I know a quality electric fan is better, but I just flat out don't have the cash for a good electric.
Brady

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1992 Camaro RS - 355 and 3.73s (http://www.thirdgen.org/rides/index.tgo?action=view&rideid=8390)

Click here for pictures and some videos. (http://briefcase.yahoo.com/brodyscamaro)

Ive had two different type of flex fans. One was a PAW performance fan (the one that has the edges of the blades bent at 90 deg angles) but it came apart at 5000RPM's and did major damage to the radiator, shroud hoses etc. I went to the Perma-Cool Heavy Duty RV Flex Fan but after a couple of years of listening to the fan at 2000-3000 RPM's while cruzing drove me nuts (The fan noise was louder than the engine and exhaust!)

I finally switched over to the Windstar dual electric and love it. There was a test comparison done by Car Craft 1 or 2 years ago that said a properly operating clutch fan was the best for cooling using minimum HP.

My flex fan is fine. It hasent come apart and doesnt look like that gonna happen either. i duno your call

This will be long, but I think it will be worth it! Bear with me please...this is my professional opinion about the product as an engineer.

I have researched this a couple of years ago and here is what I found. I am going to do an article sometime this year in the Northern and Southern Rodder Mags on it too. I have to update some of the information before completing the article however.

Derale has re-engineered the flex fan. I was NOT a fan (no pun intended) of ANY flex fan until a couple of years ago Derale came out with this series (Part number 17XXX). I was given a discertation on flex technology by an engineer at Derale that proved to me that they knew what they were doing. He provided me with a sample to test against any competitor or fixed/clutched fans as well. I went in skeptical as heck, but my engineering analysis changed my mind.


The problem with most old technology flex fans and their designs was that they are still embedded in the original founding concept and design(s) that they are going to take less power all the way around. This was the founding approach to producingthese products.

This inherent design issue(s) caused these problems:

1. Flex fans do not have the pitch or the blade area to support large CFM numbers down low....in other words ability to cool at idle and slow speeds is crummy at best. Just look at them and this will tell you this problem. They are wanted to reduce the drag on the engine therefore that makes sense?

2. Because of their light weight construction they commonly did not use methods of construction and or materials (that increased weight) to keep their blades hooked up to the hub or longivity under duress. This includes the use of light weight rivots, aluminum and plastic blades or very soft steel alloys, which is a real no-no, whereas aluminum/plastic and other light weight allows with little or no other support will "woller" out the rivot holes and eventually fail...making ram air vents in the hood whether you want it or not.

3. The use of aluminum and plastic blades and soft alloys will also cause fatigue quickly causing additional cracking around the rivots or other stress points again making for flying objects under the hood.

4. The inherent designs where in fact produced for short term use and not long term use.

5. With the RPM range of performance engines these days these products where not designed to take the kind of abuse of floggin that thumper at 6000 all the time! Another attachment and reliability problem!...And you know what happens from there, need I say more?

I can't really speak to all the designs of all the flex fans out there, but I do know after meeting the Derale engineer at SEMA a few years back and his design discertation on the fan that I recommended, it's a superior product to anything that I know out there unless I missed something. These are the reasons why from strictly an analysis point of view:

1. The heavy duty series fan is NOT designed to be a "lightweight" solution to reducing drag at low engine speeds. The fan is quite heavy...almost as heavy as a regular big block mechanical fan but certainly a lightweight compared to a fan and clutch assembly. The hub in fact is a hardened steel hub. The fan is however designed to give up all it's drag above 3000 rpms to significantly reduce drag. YOu cannot hear it above that like regular flex fans because of its design efficiency.

2. The attachment technology is just like the regular mechanical fans with full frontal support for the stainless steel blades (check out the picture in my first post) and moreover "entrapment" fastening methodogy which guarantees not only the rivots will NOt take all the force but the blades do not move whatsoever. This method is seven times stronger than the usual and customary attachment technologies used in flex fans of other designs. In other words...it won't/can't launch blades.

3. The stainless steel blades are a higher quality of stainless that can be bent to move more air at lower speeds, but can be pushed back with centrifugal force and drag to "give it up" at higher engine speeds. This higher strength stainless will take substantially more rpms (up to 15k) and will not crack and "woller" at all. The blades are actually thinner, but stronger. This allows maximum cooling air at idle and slow speeds, but less drag at higher rpms.

This combination of new technology and design is a killer product, especially for the money! I have been testing one on my 69 Camaro for two years of floggin that 400hp+ small block to 7000rpms, plus airconditioning and Atlanta traffic....and it cools great, very little noise, and I recently Xrayed the sucker over at the aviation hanger and no stress cracks or wear apparent.

I recently recommended the fan to a fellow that has a 69 SS Chevelle with air that was having problems cooling in Atlanta traffic. He took the fixed fan and clutch off to replace with a 18" chrome and stainless steel bladed monster. Not only did he fix his cooling problem, he gets better milage and says that the "seat of the pants feel" at higher rpm is better. Says it chirps the tires now longer when shifting up! So, go figure.

I will say that I am NOT the expert on all the fans that are out there....just have examined the subject and drawn certain conclusions. My recommendation is to avoid:

1. Any flex fan with small blades and/or high angle bending of the blades which create stress along those bends. Plus they will NOT cool at idle and slow speeds.

2. Any flex fans (including the other Derale models) that a made from aluminum, plastic, or soft steel alloys.

3. Any flex fans with just rivots as attachments methodology.

4. Any flex fans constructed without blade support of some kind on the leading edges of the blades.


Waaaaaaaaay toooooooo much information....I apologise for the length, but I hope someone can glean some good information from this.


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Steve "Jack'stands" Jack
Tech forum at www.inccn.net/techforum.htm (http://www.inccn.net/techforum.htm)

Thanks. I will be getting a 17" Heavy Duty Derale Flex Fan with a 2" spacer. Thanks for the information.
Brady

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1992 Camaro RS - 355 and 3.73s (http://www.thirdgen.org/rides/index.tgo?action=view&rideid=8390)

Click here for pictures and some videos. (http://briefcase.yahoo.com/brodyscamaro)

<BLOCKQUOTE>quote:</font><HR>Originally posted by HOTRODSRJ:
The fan is however designed to give up all it's drag above 3000 rpms to significantly reduce drag. YOu cannot hear it above that like regular flex fans because of its design efficiency.<HR></BLOCKQUOTE>I cruise on the higway at 2600 RPMS (70 MPH). I'm sure there will be some noise, but will it be great?

Some great info there Steve... thanks!

Olli

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[O]==+==[O]
Team Member #1920
71 2-door Chevelle Malibu (http://www.donmega.de)

"You can't impregnate me with all your foreign words!!"

Why can't you spend the $30 and and get a new fan motor? Don't be such a tight wad, you'll like the end product if you do it right the first time. Just my $0.02

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For Sale: Headers for 68-72 Chevelle/ El Camino for Small Block

<BLOCKQUOTE>quote:</font><HR>Originally posted by SDuster11:
Why can't you spend the $30 and and get a new fan motor? Don't be such a tight wad, you'll like the end product if you do it right the first time. Just my $0.02

<HR></BLOCKQUOTE>Well, I could go out a buy a $30 dollar fan motor, but then what do I have? A hot small block come summer time that's what. The single electric fan could not keep the 305 cool in stop and go traffic in summer heat, how is that fan going to keep the 355 cool? I'd rather lose 10 HP and NEVER have to worry about the temp.; wouldn't matter if it was 100+ degrees with 100% humidity in stop and go traffic. The crappy single fan sucks. Why spend $30 and have a cooling problem come March? Besides the Derale HD Flex Fan and 2" Spacer will be here the 26th or the 27th http://www.chevelles.com/forum/biggrin.gif



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1992 Camaro RS - 355 and 3.73s (http://www.thirdgen.org/rides/index.tgo?action=view&rideid=8390)

Click here for pictures and some videos. (http://briefcase.yahoo.com/brodyscamaro)