Flex fans, pluses and minuses????
Thread Starter
Burning Brakes
Joined: Jun 2009
Posts: 840
Likes: 4
From: Syracuse IN
Flex fans, pluses and minuses????
I am pulling out the L81 in the vette next week and replacing with a Vortec 383. The new engine is set up utilizing a serpentine belt sytem. I have used this exact system on my CJ. Since the Serpentive belt will use a reverse rotation water pump, the stock style fan will not work. I have been running a flex fan on the CJ engine for many years without any problems. I have been hearing negitive comments on the board about flex fans, Why??? Please educate me. I am comfortable using a flex fan but if any other ways are better, please let me know. thanks Al
Burning Brakes
Joined: Feb 2004
Posts: 924
Likes: 2
From: Kearneysville West Virginia
You will hear a lot of negative comments about flex fans. My 69 GTO came from the factory with one, and when I sold it almost 40 years later, it still had the original flex fan with 175,000 miles on it, no problems. I have never had a problem with them.
Thread Starter
Burning Brakes
Joined: Jun 2009
Posts: 840
Likes: 4
From: Syracuse IN
The flex fan I have been using is rated at up to 10,000 rpm. We routienly run it up to 7,000 on hill climbs and 3,500 constant on the hiway. I am not sure how loud they are though. I don't think the fan RPM is as fast as Crank rpm is. The pully is larger on the water pump than the crank pulley. If I had to I could transfer all of the bolt on equipement, ie, water pump, power steering, alternator ect off of the L81 onto the new engine. The new engine comes complete including MPI. I just hope it will fit under the hood. I still need to measure for clearance. Al
Drifting
Joined: Aug 2005
Posts: 1,682
Likes: 3
From: League City TX
I have seen OEM solid fans with no clutches, but I cant ever remember seeing a factory fan with flexible blades.
Melting Slicks
Joined: Mar 2008
Posts: 2,666
Likes: 289
From: Spring Park MN
I ran a 10,000 rpm rated flex fan for a long time and routinely ran it up to 7500 rpm with no problems. There is some cheap junk out there though. If you have to run one make sure it a name brand and it is rated at a much higher rpm than it will ever see.
I much prefer electric fans, but I also understand sometimes they are not in the budget.
Le Mans Master
Joined: Oct 2007
Posts: 7,430
Likes: 958
From: Tennessee/Rhode Island
Flex fans are god awfully loud and can fly apart destroying everything in sight. I would not use one unless you had no other alternative!
Last edited by jb78L-82; Dec 17, 2010 at 07:01 PM.
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Thread Starter
Burning Brakes
Joined: Jun 2009
Posts: 840
Likes: 4
From: Syracuse IN
I just don't hear any extream noise from the flex a lite unit we use in the Cj I am not concerned at all of the integrity. The mass of an OEM clutch and fan is alot more than the aluminum. If I could use a very good electric I would not even use a mechanical. Al
Burning Brakes
Joined: Feb 2004
Posts: 924
Likes: 2
From: Kearneysville West Virginia
Instructor
Joined: Jul 2003
Posts: 156
Likes: 0
From: methuen ma
Safety Car
Joined: Aug 2001
Posts: 4,883
Likes: 11
From: North Easton Mass
Why don't you just start with using the original electric fan and see how it works before making any changes? A higher HP motor doesn't necessarily mean that it is going to run hotter. It all depends on the individual engine and how it is tuned.
My LS1 engine has more than twice the HP of the origonal 350 and I am using the same Dewitt's radiator that I bought as a replacement for the original radiator. The car runs no hotter, and in most cases cooler than the original engine did.
Rick B.
My LS1 engine has more than twice the HP of the origonal 350 and I am using the same Dewitt's radiator that I bought as a replacement for the original radiator. The car runs no hotter, and in most cases cooler than the original engine did.
Rick B.
Burning Brakes
Joined: Oct 2003
Posts: 1,090
Likes: 74
From: New Carlisle IN
My 76 had a flex fan on it when I bought it about 5 years ago. It alwyas ran hot, but not excessivley so. I had always ment to put the stock fan back on, but never got around to it. Well this last summer, the car would continually hit 240*. I tried flushing the radiator, taking out the unused AC condenser, water wetter, and a few other things. None of it worked. I then decided to try putting on the stock fan from my 73 that had a very worn out clutch. As soon as I put that on, the car never saw over 210*. I then bought a new clutch and now it is hard for me to get the car over 180*. Even when I make back-to-back-to-back autocross runs. I will never put another flex fan on any of my cars.
Drifting
Joined: Mar 2007
Posts: 1,936
Likes: 1
From: Winston-Salem NC
Try this for some info http://www.corvettefever.com/techart...engine_fan/ind
ex.html
ex.html
Not a good link. Sounds like a great article!
Le Mans Master
Joined: Dec 2003
Posts: 5,727
Likes: 38
From: Fremont CA
Due to my 440 Six Pack Mopar's 18" stainless steel flex fan, I am scarred for life. I sliced my middle finger wide open on it during a camshaft break-in back in 1978-79 trying to add water to the radiator. I was transported the the Emergency Ward in my buddies chop top Model A and billed $96 for 8 stitches by the hospital (I bet ir would be 3grand today for the same work.)
I run the factory clutch fan (5 blade HP model) on my 7000 RPM LT-1 motor but, my Jeep TJ has an electric fan for rock crawling on it.
Flex fans are no longer included in any of my automotive builds.
I run the factory clutch fan (5 blade HP model) on my 7000 RPM LT-1 motor but, my Jeep TJ has an electric fan for rock crawling on it.
Flex fans are no longer included in any of my automotive builds.
Thread Starter
Burning Brakes
Joined: Jun 2009
Posts: 840
Likes: 4
From: Syracuse IN
Wow, that is the exact fan I have on my other build, CJ 7 383. Maybe the total electric would be a better choice. Worse case I would need a Reverse rotation, clutch and fan. Al
Advanced
Joined: Feb 2009
Posts: 64
Likes: 3
From: Blairstown NJ
I've seen two of them lose blades,one on a Camaro 396 and on my '79 Vette. Both went thru the shroud. The one in the Camaro went thru the hood, mine just put a big ding in the fiberglass. I'll never use one again.
Le Mans Master
Joined: May 2006
Posts: 9,993
Likes: 1,136
From: League City Tx
Flex fans are junk. Unless you found a good one from the 70s that is still alive...
Stick with the 7 blade and thermal clutch.
Better yet, go electric if there is anyway you can squeeze it in the budget. More HP, better cooling, better fuel mileage.
Stick with the 7 blade and thermal clutch.
Better yet, go electric if there is anyway you can squeeze it in the budget. More HP, better cooling, better fuel mileage.
Safety Car
Joined: Nov 2008
Posts: 3,713
Likes: 550
From: Seattle Washington
About 20 Years ago Hot Rod magazine had a Dyno Test on both HP and Cooling useing all popular Fans and guess one won? The Stock won won Cooling hands down and even edged out the Electric and the Flex in HP.
I'd say the ECU has improved the Electric since. Why not just bolt the stock Fan on Backwards for a Left Hand Pump??
I'd say the ECU has improved the Electric since. Why not just bolt the stock Fan on Backwards for a Left Hand Pump??