clutch fan vs. flex fan for fuel eco. - The 1947 - Present Chevrolet & GMC Truck Message Board Network

ol yellow 72 · 01-02-2011, 05:05 PM

simple question im running a flex fan on my 350 with a 3 inch spacer. would i gain fuel mileage if i swap back over to a stock clutch fan setup?

Tx Firefighter · 01-02-2011, 05:11 PM

Absolutely

Restrorob · 01-02-2011, 05:49 PM

^^^^ without a doubt.....

mooseknuckles · 01-02-2011, 05:51 PM

....and maybe a little bit of hp!

3r!c84 · 01-02-2011, 05:52 PM

flex fans have a bad rep for falling apart and going threw the hood and rad. not so safe. id put back the stock one!

benoit454 · 01-02-2011, 06:06 PM

yea everyone says that and we've had them for years and ran them past 7l rpms never a problem. Not to mention they cool better then clutch type. always have for me.

As for constant drag and freeing up accessories, yea they will and it will add maybe a hp or 2 if you're lucky and you might get a 1 mpg improvment if that.

IMO you want to save power and gas, get electric fans.

baclay9 · 01-02-2011, 06:07 PM

When buying a clutch for a clutch fan do you want the regular one or a thermal one?
Posted via Mobile Device

ol yellow 72 · 01-02-2011, 06:16 PM

thanks guys for a quick responce, looks like im hitting the junk yard tommorow

dmartin1 · 01-02-2011, 07:52 PM

i got dual electric fans set-up and the radiator mount and all for them for 50$ all together,the front of the engine looks amazingly better,i imagine my gas mileage has rose,and they cool it great!

benoit454 · 01-02-2011, 08:48 PM

no doubt e fans really clean it up underhood for sure. More room and cleaner.

355GoldieGM · 01-05-2011, 12:04 AM

Quote:

Originally Posted by dmartin1

i got dual electric fans set-up and the radiator mount and all for them for 50$ all together,the front of the engine looks amazingly better,i imagine my gas mileage has rose,and they cool it great!

is that a kit you got?? and if so where at?? 50 bucks is cheap for dual fans!!

bigblock73 · 01-05-2011, 12:29 AM

I ran a flex fan once, never again...didn't keep the truck cool enough (and they look cheap). Put on a new stock clutch fan, NEVER had an issue. Couldn't tell a power or mileage diff with either, the peace of mind was "cool" enough for me. Elec fans are nice, but I prefer the simplicity of a clutch, and they are easier to put in.

Gordonr1973 · 01-05-2011, 02:32 AM

Quote:

Originally Posted by bigblock73

I ran a flex fan once, never again...didn't keep the truck cool enough (and they look cheap). Put on a new stock clutch fan, NEVER had an issue. Couldn't tell a power or mileage diff with either, the peace of mind was "cool" enough for me. Elec fans are nice, but I prefer the simplicity of a clutch, and they are easier to put in.

Would you keep a stock clutch fan in the case of a LS swap? (Sorry, not trying to hijack the thread, just weave it a bit)

http://67-72chevytrucks.com/vboard/s...d.php?t=419809

http://67-72chevytrucks.com/vboard/s...d.php?t=414820

benoit454 · 01-05-2011, 02:15 PM

I had the exact opposite happen then what jeff had....

I had my monte carlo ss and nothing changed other then the fans, ran a clutch fan because everyone said how much better it was, wrong, the thing over heated. Now don't jump in and say oh the clutch was bad, again wrong, the clutch was working perfectly and kept my old mans 86 k10 cool with a/c all day long idleing in traffic. Mine jumped up to over 250 and popped the upper radiator hose. It blew it off the thermostat housing, and it was tight. I bought a flex fan and the car would never get past 180 or so in triple digit high humidity heat idleing in traffic.

The clutch fan done good in his truck, never a problem, the clutch fan in my 88 does great too, never had a problem with it.

The monte carlo had a small narrow blade 16 inch flex fan, and cooled good driving, but not in traffic, so I tried the clutch fan and it just kept creeping up while driving until it got over 250 and we were pulling off to shut it down and it started acting funny, then bam the hose blew off. I bought a wide blade 18 inch flex fan and it never got past 180 or 190 again. I had either a 160 or 180 t-stat in it I forget which.

So honestly I think if you got a flex fan and it works great, keep it, swapping might hurt it, like it did me.

If you got a clutch fan and it works good, keep it.

If you got a flex fan and it doesn't cool good, see what size it is, and the blades, narrow or wide, if they are narrow go with wide, if it's small get the biggest you can fit in your shroud.

If you got a clutch fan that's not working good, check the clutch or change it, if it works get a big flex fan with wide blades.

That's if you want mech. fan, if not then any of the above go with electric to save fuel and drag on the engine. I have yet to swap to electric but would like to, just afraid of it not cooling enough, but I know if you get the right fans it will. If they can cool a v8 camaro with like no grille opening for air, it should cool a truck with a huge grille area for sure.

bigblock73 · 01-05-2011, 02:23 PM

Chris, what you mentioned and I am sure you may know about...is that the fan (clutch or flex), needs to be positioned properly in the shroud. I assume this could be several peoples problems or phobias about each one way or another.

bigblock73 · 01-05-2011, 02:23 PM

Quote:

Originally Posted by Gordonr1973

Would you keep a stock clutch fan in the case of a LS swap? (Sorry, not trying to hijack the thread, just weave it a bit)

http://67-72chevytrucks.com/vboard/s...d.php?t=419809

http://67-72chevytrucks.com/vboard/s...d.php?t=414820

Never gave it any thought, I can't really give you a good answer.

ironroad9c1 · 02-04-2011, 01:07 PM

Always run a Thermal clutch fan. You couldn't give me a POS flex fan, they are a crutch , If you have to have a flex fan to stay cool, then you have other problems.

Shawn5488 · 02-04-2011, 08:55 PM

Always use a stock fan and fan shroud, try to get a RV or snow plow prep clutch as they will engage lower and harder for better cooling.

mooseknuckles · 02-04-2011, 08:56 PM

dual electric's the way to go!

burger · 02-08-2011, 01:16 PM

Quote:

Originally Posted by dmartin1

i got dual electric fans set-up and the radiator mount and all for them for 50$ all together,the front of the engine looks amazingly better,i imagine my gas mileage has rose,and they cool it great!

Do you have pictures of your setup? I assume you pulled this from the junkyard. What was the original application?

Thanks,
Ed

johnnypop · 02-08-2011, 08:40 PM

I have dual electric fans and they work amazing... Popped a fuse once, but now I carry spare fuses and haven't had it happen since. Idling up and down 4x4 trails in 90 degree heat, romping it on the same trails, cruising down the freeway, pulling up grades... always stays put.

3r!c84 · 02-08-2011, 09:16 PM

johnnypop what fans are you using. and what relay

johnnypop · 02-08-2011, 10:38 PM

They're dual 13.5" flex-a-lite fans, the relay is built into/mounted to the fan shroud and came with the kit... they call it the variable speed control module on their website.

01-02-2011, 05:05 PM	#1
ol yellow 72 Registered User Join Date: Aug 2005 Location: kentucky Posts: 210	clutch fan vs. flex fan for fuel eco. simple question im running a flex fan on my 350 with a 3 inch spacer. would i gain fuel mileage if i swap back over to a stock clutch fan setup?

01-02-2011, 05:11 PM	#2
Tx Firefighter Watch out for your cornhole ! Join Date: Jun 2003 Location: Azle, Texas Posts: 14,162	Re: clutch fan vs. flex fan for fuel eco. Absolutely __________________ I'm on the Instagram- @Gearhead_Kevin

01-02-2011, 05:49 PM	#3
Restrorob The One And Only !!! Join Date: Jan 2007 Location: Hole in the woods Florida Posts: 4,567	Re: clutch fan vs. flex fan for fuel eco. ^^^^ without a doubt..... __________________ 93 Jeep XJ 88 Buick La Sabra Toys; 88 TA-GTA in the works.... 97 GMC Ext. Cab 502 Crate 5 Spd......Sucks Gas But Haulz Azz ! The primary function of an Engineer is to make it difficult for the Fabricator and impossible for the Mechanic. *"Why go out preserved when you can go out beat up, worn out, sliding in sideways screaming, Holy Sh!t What A Ride" !!!*

01-02-2011, 05:51 PM	#4
mooseknuckles Registered User Join Date: Sep 2009 Location: ottawa,canada Posts: 4,550	Re: clutch fan vs. flex fan for fuel eco. ....and maybe a little bit of hp! __________________ my build threads '86 C10 http://67-72chevytrucks.com/vboard/s...d.php?t=415628 '67 C10 http://67-72chevytrucks.com/vboard/s...d.php?t=635078 '63 GMC http://67-72chevytrucks.com/vboard/s...d.php?t=674682

01-02-2011, 05:52 PM	#5
3r!c84 Badass Join Date: Jan 2009 Location: lox. fl Posts: 4,586	Re: clutch fan vs. flex fan for fuel eco. flex fans have a bad rep for falling apart and going threw the hood and rad. not so safe. id put back the stock one! __________________ Think outside the box? -84c10 (1stcar)→My Build← -00 Saturn 5spd drop a gear and disappear! 1/4:13:90

01-02-2011, 06:06 PM	#6
benoit454 Chris Join Date: Nov 2004 Location: Monaville, WV Posts: 3,737	Re: clutch fan vs. flex fan for fuel eco. yea everyone says that and we've had them for years and ran them past 7l rpms never a problem. Not to mention they cool better then clutch type. always have for me. As for constant drag and freeing up accessories, yea they will and it will add maybe a hp or 2 if you're lucky and you might get a 1 mpg improvment if that. IMO you want to save power and gas, get electric fans. __________________ Chris GIT R DONE!!!!!! Check out all our rides, http://www.cardomain.com/id/benwa454

01-02-2011, 06:07 PM	#7
baclay9 Registered User Join Date: Apr 2010 Location: Newcastle, OK Posts: 1,344	Re: clutch fan vs. flex fan for fuel eco. When buying a clutch for a clutch fan do you want the regular one or a thermal one? Posted via Mobile Device

01-02-2011, 06:16 PM	#8
ol yellow 72 Registered User Join Date: Aug 2005 Location: kentucky Posts: 210	Re: clutch fan vs. flex fan for fuel eco. thanks guys for a quick responce, looks like im hitting the junk yard tommorow

01-02-2011, 07:52 PM	#9
dmartin1 Registered User Join Date: Aug 2008 Location: mohave valley,arizona Posts: 1,088	Re: clutch fan vs. flex fan for fuel eco. i got dual electric fans set-up and the radiator mount and all for them for 50$ all together,the front of the engine looks amazingly better,i imagine my gas mileage has rose,and they cool it great! __________________ 1969 Shortbed in progress 1982 short step, few suspension and motor upgrades.getting a 468 1978 Shortbed fleet side bonanza fully loaded 1978 k20 Silverado loaded.currently engine-less 1989 k10 suburban 9" lift 65 nova And more

01-02-2011, 08:48 PM	#10
benoit454 Chris Join Date: Nov 2004 Location: Monaville, WV Posts: 3,737	Re: clutch fan vs. flex fan for fuel eco. no doubt e fans really clean it up underhood for sure. More room and cleaner. __________________ Chris GIT R DONE!!!!!! Check out all our rides, http://www.cardomain.com/id/benwa454

01-05-2011, 12:29 AM	#12
bigblock73 yeller Join Date: Oct 2001 Location: Twin Cities Posts: 13,824	Re: clutch fan vs. flex fan for fuel eco. I ran a flex fan once, never again...didn't keep the truck cool enough (and they look cheap). Put on a new stock clutch fan, NEVER had an issue. Couldn't tell a power or mileage diff with either, the peace of mind was "cool" enough for me. Elec fans are nice, but I prefer the simplicity of a clutch, and they are easier to put in. __________________ Jeff 73-87.com 73-87.com Facebook page 73-87 cab corner 6x9 speaker brackets for sale 67-72 cab corner speaker brackets for sale 47-54 cab corner speaker brackets for sale

01-05-2011, 02:15 PM	#14
benoit454 Chris Join Date: Nov 2004 Location: Monaville, WV Posts: 3,737	Re: clutch fan vs. flex fan for fuel eco. I had the exact opposite happen then what jeff had.... I had my monte carlo ss and nothing changed other then the fans, ran a clutch fan because everyone said how much better it was, wrong, the thing over heated. Now don't jump in and say oh the clutch was bad, again wrong, the clutch was working perfectly and kept my old mans 86 k10 cool with a/c all day long idleing in traffic. Mine jumped up to over 250 and popped the upper radiator hose. It blew it off the thermostat housing, and it was tight. I bought a flex fan and the car would never get past 180 or so in triple digit high humidity heat idleing in traffic. The clutch fan done good in his truck, never a problem, the clutch fan in my 88 does great too, never had a problem with it. The monte carlo had a small narrow blade 16 inch flex fan, and cooled good driving, but not in traffic, so I tried the clutch fan and it just kept creeping up while driving until it got over 250 and we were pulling off to shut it down and it started acting funny, then bam the hose blew off. I bought a wide blade 18 inch flex fan and it never got past 180 or 190 again. I had either a 160 or 180 t-stat in it I forget which. So honestly I think if you got a flex fan and it works great, keep it, swapping might hurt it, like it did me. If you got a clutch fan and it works good, keep it. If you got a flex fan and it doesn't cool good, see what size it is, and the blades, narrow or wide, if they are narrow go with wide, if it's small get the biggest you can fit in your shroud. If you got a clutch fan that's not working good, check the clutch or change it, if it works get a big flex fan with wide blades. That's if you want mech. fan, if not then any of the above go with electric to save fuel and drag on the engine. I have yet to swap to electric but would like to, just afraid of it not cooling enough, but I know if you get the right fans it will. If they can cool a v8 camaro with like no grille opening for air, it should cool a truck with a huge grille area for sure. __________________ Chris GIT R DONE!!!!!! Check out all our rides, http://www.cardomain.com/id/benwa454

01-05-2011, 02:23 PM	#15
bigblock73 yeller Join Date: Oct 2001 Location: Twin Cities Posts: 13,824	Re: clutch fan vs. flex fan for fuel eco. Chris, what you mentioned and I am sure you may know about...is that the fan (clutch or flex), needs to be positioned properly in the shroud. I assume this could be several peoples problems or phobias about each one way or another. __________________ Jeff 73-87.com 73-87.com Facebook page 73-87 cab corner 6x9 speaker brackets for sale 67-72 cab corner speaker brackets for sale 47-54 cab corner speaker brackets for sale

02-04-2011, 01:07 PM	#17
ironroad9c1 Master Hater Join Date: Apr 2006 Location: Temple,Tx. Posts: 402	Re: clutch fan vs. flex fan for fuel eco. Always run a Thermal clutch fan. You couldn't give me a POS flex fan, they are a crutch , If you have to have a flex fan to stay cool, then you have other problems. __________________ 1997 C1500 ECSB 4.3/NV3500 8.5 3.42 "This evening, all of you bleeding hearts... why don't just go ahead and hug yourself for the next 20 minutes or so, because there's a really good chance you're gonna be offended".- Captain Owen Honors

02-04-2011, 08:55 PM	#18
Shawn5488 Registered User Join Date: Jul 2010 Location: Central IN Posts: 87	Re: clutch fan vs. flex fan for fuel eco. Always use a stock fan and fan shroud, try to get a RV or snow plow prep clutch as they will engage lower and harder for better cooling.



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02-04-2011, 08:56 PM	#19
mooseknuckles Registered User Join Date: Sep 2009 Location: ottawa,canada Posts: 4,550	Re: clutch fan vs. flex fan for fuel eco. dual electric's the way to go! __________________ my build threads '86 C10 http://67-72chevytrucks.com/vboard/s...d.php?t=415628 '67 C10 http://67-72chevytrucks.com/vboard/s...d.php?t=635078 '63 GMC http://67-72chevytrucks.com/vboard/s...d.php?t=674682

02-08-2011, 08:40 PM	#21
johnnypop Registered User Join Date: Apr 2010 Location: San Jose, CA Posts: 46	Re: clutch fan vs. flex fan for fuel eco. I have dual electric fans and they work amazing... Popped a fuse once, but now I carry spare fuses and haven't had it happen since. Idling up and down 4x4 trails in 90 degree heat, romping it on the same trails, cruising down the freeway, pulling up grades... always stays put.

02-08-2011, 09:16 PM	#22
3r!c84 Badass Join Date: Jan 2009 Location: lox. fl Posts: 4,586	Re: clutch fan vs. flex fan for fuel eco. johnnypop what fans are you using. and what relay __________________ Think outside the box? -84c10 (1stcar)→My Build← -00 Saturn 5spd drop a gear and disappear! 1/4:13:90

02-08-2011, 10:38 PM	#23
johnnypop Registered User Join Date: Apr 2010 Location: San Jose, CA Posts: 46	Re: clutch fan vs. flex fan for fuel eco. They're dual 13.5" flex-a-lite fans, the relay is built into/mounted to the fan shroud and came with the kit... they call it the variable speed control module on their website.

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