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Flex Fan



Well, we bought a metal flex fan/spacer and replaced the fan clutch. I have driven it to work, and around town, for a week and I also took a quick jaunt to a neighboring town 30mi. away.

My findings:
1 The flex fan MOVES the air! Noticeable difference.
2 The flex fan has more noise, but not the whine I expected, it is more like a deep roar.
3 I don't notice noise under 45mph and normal driving. If I put my foot in it, you definitely hear it, and at hwy speeds above 45 it is noticeable. (un-noticeable with radio on)
4 I had Hubby drive it past the driveway (country road speed limit of 55..accelerating hard from a stop, driving past and driving past again with a quick spurt of acceleration) so I could hear how it sounded. Actually sounded like I had a bigger engine in it.
5 Around town temp stayed at 185. 1 hour trip, temp ranged to 195 when driving hard, cooling down to 185 as we slowed driving speed. Never reached 200.

Overall, the sound is like the engine is running at a higher rpm than it actually is. It just sounds like it is working harder, I can tell by the rpm guage it is not. I have been pleased with the temp results. This weekend will be the test. I just picked up the correct length AC belt, and we will replace the stretched one this weekend...I want to see what temp 78 will run with the AC on, and I'll report back with our findings.
Replaced AC belt for correct fit

Former AC belt had too much play in it, and slipped/squealed badly. We replaced the belt today, and I drove to the next town for some shopping, about 25mi. away. 78 did just fine with the AC on! Temp stayed under 190, climbed to 195 when driving under 35mph, but cooled back to 185 when driving 45mph. I am very pleased.
I also heard an exhaust leak...when I checked it out, my hose that runs to the exhaust breather tube had broken off just above the clamp. Will repair this evening when she's cooled down.
You go girl...


You're turning in quite the "wrench" :cool
(and yes I spelled it korectly) ;)

Bet Ken is really proud of you. :)

Hello there Silver 78. Who did you purchase the
flex fan from? And did you also replace the clutch or did the flex fan remove the need for the clutch?

Thanks for your reponse!
Hello K Lietzel

I bet your sunflower-yellow Vette sure looks pretty!

When you put on a flex fan, the old fan and it's clutch need to be removed. Installing a flex fan eliminates the need for the fan clutch, as this new fan will be driven directly by the motor's rpm's. A spacer for the flex fan needs to be purchased, also. This spacer takes up the room the fan clutch used, and keeps your flex fan blades where they need to be, inside the shroud.

I purchased our parts at Barry's Speed Shop here in Monroe, GA. They were made by Flex-a-lite.
The fan part # is 1318, standard 18" rotation.
The spacer part # is 14538, specific for Chevrolet Corvette applications.

Be certain the spacer you purchase has the 3/4" female pilot hole and a thickness of 2".

Be warned...the spacer kit (flex-a-lite) we purchased, came in two pieces...and they did NOT want to stay lined up while we were leaning over the fenders trying to start the bolts!!! After some colorful words on Hubby's part, ;), I used electrical tape to hold the pieces together, lined it up on it's mounting position on the front of the engine, and again taped it in place so we could both work on opposite sides and finger turn in the mounting bolts. Saves Hubby loads of frustration if I can be helpful!

Overall, I am very pleased with the flex fan's performance! Let us know how it works for you if you decide to try it!
Silver /Heidi
flex fan

I thought flex fans were for dragging

keeping the engine cool while your at idle and reducing drag caused by the fan as revs increase.

If you look at the fan at idle the then rev the engine about 1000 rpms or more you can see that the fan blades flatten out, which means it pulls less air across the radiator. The maintained temp could be explained because your car is moving and air is being pulled across the radiator.

It is not to say they are bad, in fact I put one in my car (it now has dual electric fans). I am just pointing out that they are not necessarely the answer to overheating cars as I was once duped by this.

Good point...

Overheating can be caused by any number of things.

However, for my particular application, it works for me. I had been afraid to run my AC because it would cause the 78 to run at 240 degrees! :eek Now I can use the AC without fear of driving too slow, or too fast and causing it to run hot or overheat. :)

I also noticed an overall temp decrease of between 10-15 degrees at all speeds. Before, if I ran the 78 hard, she would reach temps of about 205-210. Now running hard she may get to 195, and never sees 200. So drawing from these immediate results...I probably had a bad fan clutch. (however, all fan clutches we've installed/replaced (5 or 6 over 11 yrs) ran at 195-210 degrees with either a 180 or 190 thermostat) Regardless, the flex fan definitely improved overall engine temperatures for me.

Flex fan

Hello again Silver 78.

Thanks for all the info and part numbers for your flex fan conversion. My '72 has no history of overheating -- yet! Every day is an adventure with these 30 year old cars!
I have a 10,000 rpm Stainless Steel large blade 17.5 inch fan from Jeg's and the two inch spacer. They move allot more air and are safety rated. The fan is less than $40. The fan is driven much more rpm than the motor. So any of you guys exceeding 6000 rpm should consider the switch.

I was looking for less rotational weight so the clutch fan had to go. I have also never spit the belts off since the change.

Your 79 is wearing the rear spoiler I want!
Please tell me where you purchased it!!! In catalogs, I have only seen them for the 80-82's, and they have the rear 'flip' that is taken into account for mounting.
BTW, your Green Machine is beautiful! (however, the CACC has size requirements for signature pictures...one of the Moderators will be along shortly to direct you to their guidelines)
Another factor on the flex fan vs. fan clutch is power and torque. I recently had my vette on the dyno when the mechanic noticed that my fan clutch was not releasing at high rpm. I have a new fan clutch with less than 1000 miles on it. So the mechanic decided to remove the clutch and fan and do another pull. The difference was 12.6 hp and 17.5 ft/lbs of torque. Thats alot! I plan to add a flex fan until I can budget in dual electic fans.



I thought 78 seemed more "peppy"! Thought I was imagining it!
I would just like to add 2 cents to the flex fan topic! if by chance some of you are still experiencing elavated temps, there is an additive available from a company called Red Line,

it's called "water wetter" and is available at most pep boys or auto zones. THIS STUFF WORKS!!! :cool

sscam69 Is Right

I don't know how or why you're running cooler with a flex fan blade but, I do know they were designed to give more horsepower at a higher rpm because they flatten out and draw less air thus giving less resistance, more hp. I had a flex on mine and changed to a special oval track fan and it made a big difference. Another thing to consider with a flex or a clutch fan is that at some point, it will give you more power and less drag, therefore running the engine hotter. Most of these applications are for racing or high performance. If you have a driver that's running warmer than you like, my suggestion is a solid blade fan that will pull the most air all the time at any rpm. I can also tell you the after market flex fans will come apart at higher rpm's and usually one or more of the blades ends up going through the radiator. The rivets are not what the solid blade fans are made of. I ran the gauntlet of trial and error to get mine to run cooler as I've stated in many other topic posts, bottom line is you want the most air flow ALL the time unless you're looking to cut tenth's of a second of your quarter mile times which I don't think most of the posts in here are all about.
Rowdy, have you tried red line's "water wetter""?? I have used it in motorcycles and cars/trucks and like I said earlier..IT WORKS!!

I've used it, too.

I first tried Water Wetter in WA state, where 78 would run just over 210 on hot summer days (or running up the 'winding hill' to Goldendale). I did notice an apprieciable drop in temperature with its use.
Wetter Water

The first time I used it I used one bottle with no change. The second time I used it, I diluted the water antifreeze mix and used three bottles and along with a b-cool aluminum radiator I no longer have a temp problem. I'm not running anything even close to stock under the hood so I expected some heat problems. Cruising around under 3 grand, I run 180 which is what my stat is. Long hills, or grabbing full throttle gears it'll go to 190, 195 and as soon as I back out of it, the temp starts to drop back to 180.

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