Flex fan?

[69_Dream]

I recently found myself one blade shy of a fan, so...throwing around the idea of a flex fan.

I've heard good stories, but also many bad ones. You guys mind giving me some advice?

I've heard they tend to break rather easily and prematurely.

My other huge concern is cooling problems. Can they realistically cool a 427?

I've also heard they are loud, with a noise resembling a turbine. I've never heard one first hand so I really have no clue. I doubt I'd hear anything, between the engine and the hooker sidepipes So this is probably not an issue.

Still be interested to hear what everyone has to say, especially those that are running these.

Sly

 

[matchframe]

I had a flex fan on my Vette for many years. It was noticeably louder, but not annoyingly so. I doubt you will notice it much with the sidepipes right outside your door. It cooled well, but it was a small block. I also had a flex fan on my Big Block Camaro, and had overheating problems when I was in heavy traffic if it was really hot outside, like in August. Not sure how much the fan had to do with it however.

When I get my Vette back on the road, I plan to use the dual electric fans, I understand they pull alot more air through the radiator than water pump mounted fans. I do not know of any facts to back that up however.

Bill

 

[78SilvAnniv]

Flex Fan on my 78

We had summer run-hot problems in the 78 since day-one. This lasted for 9 years.

We did EVERYTHING!
New hoses, belts, t-stat, radiator, water pump, crate engine and replaced fan clutches yearly. I had fixed my AC but I did not dare use it as it shot the temp up to 240*. Summer driving was restricted to 55, anything over 60 for any length of time started the temp climbing.

When we moved to GA I was disgusted with the run-hot problem and purchased a flex fan from a speed shop. Problem solved!

Now I can drive at any speed in any weather, in town, hwy traffic or screaming around the GA mountains, WITH AC, and have yet to go over 195*. After installation, I did notice that the flexfan made more 'noise', but I decided I liked the noise because it let me know it was moving mass quantities of air. I have chambered exhaust now, and since becoming accustomed to the flexfan noise, I no longer hear it.

I love my flex fan.
Heidi

*as a caveat, it has been noted in previous posts re: flexfans that the GM cooling design should not be tampered with and nothing should be changed. Obviously, I don't agree.

 

[Copdogcorvettes]

I had a flex fan on my 78SB. worked good.but it is a bit loud. With the side pipe you should even notice it. They take a couple of HPs more to run than the clutch, but are lighter. You just need to chose one with the pitch and number of blades to fit your application. They make then in metal or fiberglass, the metal ones seam to hold up better than the fiberglass, but that is just my thought. I've had good luck with the flex fans on Jeeps. They'd keep the motor running cool at slow speeds in the mountians as well as at higher RPM's on the Hyway. 4:88 gears in a Jeep at Hyway speeds is a lot of RPM's
I have been looking at changing the fan on mine 78 with a 400SB. I'm kinda looking at the twin electics, but I've heard good and bad about that as well. So I'm not sure what I'm going to do yet.

Let us know what you do and how it works.

Gary

 

[69_Dream]

Thanks

The fan is on its way, should get it Tuesday or Wednesday.

I figure 3 responses, 3 positive answers. Good enough for me. I'll let you know how it goes, if I even notice the extra noise, and of course, cooling levels of the old vs the new.

Sly

 

[69_Dream]

Thanks

The fan is on its way, should get it Tuesday or Wednesday.

I figure 3 responses, 3 positive answers. Good enough for me. I'll let you know how it goes, if I even notice the extra noise, and of course, cooling levels of the old vs the new.

Sly

 

[Tom73]

I don't have any experence with a flex fan, my cars has the clutch set up, so I cannot speak from experence. My concern with a flex fan, if cooling is a concern, is the purpose of the flex fan. They are designed so that when you get to higher rpm the "flatten" out to reduce drag on the engine. Now if I am concerned about cooling, I do not want the fan to flatten out, I want it to keep pulling that cool air through the system. But if cooling is not a concern then it should work out okay, I guess :confused

tom...

 

[78SilvAnniv]

I believe the purpose of the flex fan is to cool at the lower speeds, where you need it. This is when you do not have the forward movement of the vehicle forcing air through the radiator.

I don't see the clutch fan set-ups doing anything different...don't they slip (could be wrong term) at certain temps and at higher rpms? If this is the case, I don't see where the function at higher rpms or speed makes any difference if they both decrease their relative effectiveness at those speeds. Of the two, I'd expect the flex fan to do more 'work' than the clutch fan set-up during higher rpm or vehicle speed. It certainly pulls more air through the radiator at slower speeds and idle.

Cooling was exactly my concern and I was able to successfully cool my engine with the first flex fan I used, after trying more than 15 new clutch fans in 12 years. We also replaced belts, hoses, t-stat, radiator, water pump and also installed a crate engine. Every troubleshoot that we tried did not fix the problem. Even the new engine had run hot problems in the summer.

The flex fan solved my run hot problems instantly. I would love to know WHY my 78 could not run cool (as GM designed) with the clutch fan.
Heidi

 

[gooney0]

least problems with flex

Flex fans are your friend. I've had all three:

Electric - the sensor's died.. then the motor died... nothing but trouble

Clutch - depends.. sometimes they stop spinning.. sometimes they lock up and always spin.. pretty hard to tell ( to a putz like me anyway )

Flex fan - always spinning, nothing to break

I actually have a clutch fan in the vette now.. but we'll see how it goes.


-Gooney0

 

[Tom73]

I believe the purpose of the flex fan is to cool at the lower speeds, where you need it. This is when you do not have the forward movement of the vehicle forcing air through the radiator.

I don't see the clutch fan set-ups doing anything different...don't they slip (could be wrong term) at certain temps and at higher rpms?

Heidi,
I know that you have had great success with a flex fan. That is great. But they were originaly developed as a performance part. They flatten out at higher engine speeds (not car speeds) to reduce pull/drain on the engine. On clutch fans, they freewheel when the temp is below a certin point and then hook up solid and rotate at all speeds after a specific temp is reached. If your engine is getting warm or hot then the clutch fan is going to pull air through the radiator. A flex fan will quit pulling air after a certin engine rpm is reached. Below that rpm the flex fan is pulling all the time no mater what the engine temp is.

tom...

 

[TWINRAY]

Have one in the '67. Haven't noticed any noise but then again the motor is pretty busy turning a 4.11 rear:s

 

[78SilvAnniv]

Sorry, Tom...

I guess I am kinda rabid on the subject of flexfan virtues. Please accept my apologies for appearing so hard-nosed about the subject.

My specific problem with my 78 was during summer high temps (CA, upper 90s low 100s) I could not drive faster than 55mph without the temp climbing well over 200*.
We tried everything and the cooling system was new or nearly new, engine tuned et cetera...I still had the same problem with the new engine.
Nothing changed for me until I installed the flexfan.

I think this is why I take such a hard line with the virtues of the flexfan over the stock clutchfan.
We tried numerous new clutchfans with no change and the first flexfan solved the problem. Part of my problem...is I don't know what the original problem was, I just have the results the flexfan gave me.

A thought...could there have been something about my pulley system that hindered the operation of the clutchfan, and now having a flexfan without the pulley system...could that be why I feel my results are so spectacular? I also thought perhaps it could have been the way the clutchfan connected to the engine, but I replaced the engine and still had the problem, so I wonder if it was a problem with my pulleys/belts creating drag?
Heidi

 

[Bob Chadwick]

The bottom line is that it worked for you Heidi, though I suspect that the solution is confusing to some since the flex fan is supposed to flatten out and pull less air at speed. I would have guessed that either your spoiler or radiator were missing seals allowing the air to go around the radiator.

My clutch fan is the original and I ran 30 miles or so yesterday at about 3000 rpm (70 - 75 mph) with the a/c on in low 90 degree heat and never got above 205. I guess I'm one of the lucky ones and if it works I'm not going to mess with it.

Bob

 

[78SilvAnniv]

Spoiler is intact, but I think it could very well have been missing seals...or not neccesarily missing seals so much as not enough seals. We are also missing the part that funnels air from the top front of the radiator to the air cleaner...need to find one.
Heidi

 

[Tom73]

We are also missing the part that funnels air from the top front of the radiator to the air cleaner...need to find one.

That could be a major issue. That space will allow ALOT of air to bypass the radiator. I would suggest cuting a foam filler for that space to see if it will help any.

tom...

 

[78SilvAnniv]

Thanks Tom,

I don't have any run hot problems now, and I think we lost the plastic funnel-to-carb thing when I did the engine swap...so it was there before and I still had the problem.
Does anyone know the proper name for that item so I can look for it without having to read every page of the catalog?
Heidi

 

[Michel73]

My 350 runs cool enough until I get on the highway (like during the Corvette Caravan or cruising with the club, 75-95mph) then it gets pretty warm 230 degrees or so. What problem do I have :confused and would a Flex Fan help?


Save the Wave

 

[Bob Chadwick]

Corvette World. 800-327-0185 calls them Air Intake Duct - Front Center. There is some confusion in my mind about which one applies. $25 - 35 plus another $10 - 15 for the flexible hose that attaches the duct to the air cleaner.

The Last Detail also appears to have it for $26 plus another $10 or so for the flexible hose.

Heidi, I go to TLD all the time. Let me know if you want me to pick it up for you and bring it to the trip.

Bob

 

[Rab563]

Michel73, in your case a flex fan would not help. Flex fans only help at very low speed conditions. My guess is that you probaly need to check the radiator for restrictions or maybe a collapsing radiator hose. Hope this helps.

Ron

 

[Michel73]

Thanks Ron for the info. I'll check this out before our Saturday Cruise.


Michel