Dual Electric Fans??? Should I switch to 7 Blade w Clutch? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

hotwls13 · 05-09-2018, 12:46 PM

I'm about a month in on my new to me 70 gmc LWB 1/2t with 350/350. I think it was setup with a camper before (some weird wiring on the firewall and some "extra" wires going back to bed). ANyway, Previous owner put in dual electric fans (no flex or 7 blade fan on my engine). They also have the fans hooked up to a toggle switch???

I've only driven the truck off the trailer and onto the side of my house. I've ran the engine a few times since then to make sure it still starts.

My questions are:

1. Shouldn't the fans be wired differently? I'm in Bakersfield, CA BAKERsfield! It will easily be over 100 degrees for like 60-90 days this summer. I need this thing to stay cool.

2. Should I just scrap the whole electric fan thing and get a 7 blade with clutch? If so, which specific one should I get for my 350? Don't care about "period correct" just want "works when it's hot outside". Hopefully not too expensive cause this is a budget build.

3. If I do put a 7 blade on, would there be any benefit to leaving the electric fans in? Sorta double dipping? Or are they just going to be in the way of eachother??

Thanks,

**HO455** · 05-09-2018, 01:14 PM

Most definitely can be wired differently. There are nice electronic controllers available to automatically operate your fans. Or if your budget is restricted there are good wrecking yard options. Before making a decision about which way to go what are your plans for the truck? Will you be in stop and go traffic? Electric fans are helpful in traffic hell. But not all electric fans are created equal. Some are up to the task of cooling a V8 others are not. Can you post some pictures of the current set up. Someone here will be able to help with determining if they will do the job. You are correct about the electric and mechanical fans interfering with each other with reduced air flow through the radiator. I believe that a Camper Special should have come with a four row radiator. Does yours have one?
Welcome aboard and let me be the first to ask for pictures.

RustyBucket · 05-09-2018, 01:53 PM

I vote for the 7 blade fan ...just my opinion. I have 7 blade clutch fans with shrouds on both of my trucks. '72 Blazer is a mild big block with fact. A/C and 4 core radiator. The '71 GMC is a mild 350 w/aftermarket A/C and an aftermarket aluminum radiator. It's HOT in central Florida and I have 160 deg. thermostats in both of them. The clutch fans run nice & quiet and cool very well. The fan blades and clutches aren't expensive and are available through chain parts stores. Good shroud makes a big difference. I'd take the electric fan off.

hotwls13 · 05-09-2018, 02:11 PM

Here are the only pics I have of radiator/fans. I can get some better ones tonight. No idea what kind of fans or radiator I have.

outfield · 05-09-2018, 02:40 PM

From the pictures it looks like you could have a HD 4 row radiator which is good. I have this radiator in my 69 K20, its stock, and with the 7 blade clutch fan and shroud it has always stayed cool, even on hot summer days and when hauling.

hotwls13 · 05-10-2018, 11:28 AM

Quote:

Originally Posted by outfield

From the pictures it looks like you could have a HD 4 row radiator which is good. I have this radiator in my 69 K20, its stock, and with the 7 blade clutch fan and shroud it has always stayed cool, even on hot summer days and when hauling.

I forgot to take more pics. How do i tell if I have a "HD 4 row radiator"? Would that have been factory or something added later?

**HO455** · 05-10-2018, 12:42 PM

A four core could of been factory. Look down into the radiator fill and count the rows of tubes across the radiator.

Here is a link to a bunch of cooling system information. The author is a little bias with his brand loyalty but overall lots of good information.

http://www.pirate4x4.com/tech/billavista/Cooling/

hotwls13 · 05-09-2018, 02:48 PM

Any links to a replacement fan/clutch? My google skills are lacking today. Keep coming up with flex fans or 7 blades for 6cyl

kenr74 · 05-09-2018, 03:40 PM

I had dual electrics on my K2500 hauler and loved them. I wired them up with temperature controllers so they came on when needed.

https://www.jegs.com/i/JEGS/555/5212...AaAleVEALw_wcB

I had one come on just above my thermostat temp and then the second came on about 20 degrees higher. I had a toggle on one of them also just as a back up but never used it.

My butt dyno said I picked up a little usable power but not sure how accurate it is.

hotwls13 · 05-09-2018, 03:54 PM

Quote:

Originally Posted by kenr74

I had dual electrics on my K2500 hauler and loved them. I wired them up with temperature controllers so they came on when needed.

https://www.jegs.com/i/JEGS/555/5212...AaAleVEALw_wcB

I had one come on just above my thermostat temp and then the second came on about 20 degrees higher. I had a toggle on one of them also just as a back up but never used it.

My butt dyno said I picked up a little usable power but not sure how accurate it is.

Wow, that looks like a really easy install. Honestly, my truck MAY have something similar. I haven't had time to go through any of the running gear. Been dealing with tank relocation, rear brakes, new wheel studs etc etc.

The previous owner (who had only had the truck for about a month and it just sat on his property) said the original owner had a camper on the truck and that he had installed these electric fans. He showed me the toggle switch to run them, so maybe it IS just a backup to manually run them?? We never got the truck up to temp so I wouldn't know if the fans kick on at that point or not.

I'll have to do some poking around and see where the wires go and if there are any probes or relays in-between.

Rufas · 05-09-2018, 05:25 PM

I vote for the fan/clutch setup. When I installed my 468 BBC I went with dual electric fans. Never could get the cooling I needed. Went back to the original fan shroud and a 7 blade fan with clutch. The fan/clutch moves much more air than the electric fans. I can place my hand just outside the grill and feel air being pulled into the radiator and that's without the fan clutch engaged.

RichardJ · 05-10-2018, 12:02 AM

Loose the old Tube & Fin Condenser and replace it with a Parallel Flow type condenser.

With the V8, I'd go with the 7-Blade clutch fan, but add an electric pusher fan in front with temp controller.
Many cry that pusher fans aren't any good, but that doesn't stop the car manufacturers, including GM from using them.
My truck has the original 4-blade and no shroud. The fan on the right side is a pusher from a '89 Cad, connected to a 208* temp switch. The fan on the left is a '94 Cad with bigger screen shield to protect my fingers at the hood release. It runs all the time the Ac is ON, which is all the time.

When I added the AC and made the mount for the new Condenser, I included the two fans at the same time as a just in case. With the 4-blade and the one pusher fan running, temps are consistent with temps before the AC.

CUDA8U · 05-10-2018, 11:03 AM

get a 4 core champion aluminum rad and add a flex a lite 180 black magic fan

brown7373 · 05-10-2018, 01:05 PM

My 72 350/350 with factory air never gets above 180-185. I live in south Florida and have NEVER had an overheating problem with a shroud, 7 blade and a clutch. If you go electric, you may need to upgrade your electrical system (charging) as they suck a lot more current than you alternator was designed for. A friend had a 454 71 Vette that ALWAYS overheated with electric fans and he ALWAYS had a weak battery. And that was after a total pro restoration. And for me, I don't like to listen to the roar of the electric fans at idle or when first shut down.

**clay68c10** · 05-10-2018, 05:15 PM

You already own the fans that are on it, give them a shot. If they work, then set up a more elaborate trigger to switch them on.
If they don't work, then go mechanical or hi-capacity electric.

That said, I ran a Lincoln MK8 fan on a 454 w/ac when I lived in TX. Even in stop and go DFW traffic with the air blasting, the eng temp never went over 205. A properly set up e-fan on a 4-core radiator will keep it cool.

hotwls13 · 05-10-2018, 05:40 PM

Quote:

Originally Posted by clay68c10

You already own the fans that are on it, give them a shot. If they work, then set up a more elaborate trigger to switch them on.
If they don't work, then go mechanical or hi-capacity electric.

That said, I ran a Lincoln MK8 fan on a 454 w/ac when I lived in TX. Even in stop and go DFW traffic with the air blasting, the eng temp never went over 205. A properly set up e-fan on a 4-core radiator will keep it cool.

I like how u think.

I was thinking the same. I'll figure out what all is going with these first. Maybe it will stay cool just the way it is.

Mollzyie · 05-10-2018, 06:17 PM

Question to u guys . Do people ditch the 7 blade fan for performance reasons ? As in like racing or 1/4 mile . Mine is long gone before I bought the truck .

68 P.O.S. · 05-23-2018, 05:09 PM

Quote:

Originally Posted by clay68c10

You already own the fans that are on it, give them a shot. If they work, then set up a more elaborate trigger to switch them on.
If they don't work, then go mechanical or hi-capacity electric.

x2

franken · 05-10-2018, 07:51 PM

Maybe dumb observations, but later trucks switched to 5 blade fans. I'm guessing GM found the effectiveness was sufficient and less blades reduced drag. Make sure the fans are pulling air through the radiator, not pushing forward.
I'd vote clutch fan for simplicity...

MARKDTN · 05-11-2018, 04:34 PM

I vote keep the electrics and do proper control. Lots of schemes to control dual fans.

hotwls13 · 05-14-2018, 12:02 PM

I was able to snap a few pics Yesterday:

ANyone know where I can get a cap for the overflow bottle? Is that a factory overflow?

68 P.O.S. · 05-23-2018, 05:15 PM

That's an aftermarket overflow bottle. These trucks didn't have a factory overflow, just a tube from the radiator to the ground. There was a dealer optioned overflow bottle. Some government trucks and whatnot could have them (same as the dealer option), but weren't available to the general public. Here's a link for some info and pics http://67-72chevytrucks.com/vboard/s...d.php?t=546610

Artofdeath · 05-23-2018, 06:29 PM

This maybe a silly question but, are the fans pushing or pulling air? They should be pulling air towards the engine. If they are pushing air towards the front of the vehicle you could have a dead zone. Just curious...

hotwls13 · 05-30-2018, 09:15 AM

Quote:

Originally Posted by Artofdeath

This maybe a silly question but, are the fans pushing or pulling air? They should be pulling air towards the engine. If they are pushing air towards the front of the vehicle you could have a dead zone. Just curious...

They are pulling air towards engine.

Rick Bollinger · 05-30-2018, 09:43 AM

My thought is set up right electric fans would be alright. But I would think that the fan mounted right on the radiator would only pull air where the fan is mounted. If it is a 10" dia fan there is only 10" of area being pulled through the radiator. If it was set back a couple of inches and set on a shroud of some sort then it would pull from the whole radiator. I had this same problem with my 68. P.O. Had it all messed up. Electric fan wired into the electric choke wire no shroud and didn't even run. I went with a LMC shroud and a 18" flex fan. It looks clean and moves lots of air. Whole set-up around $100.00

05-09-2018, 12:46 PM	#1
hotwls13 Registered User Join Date: Mar 2018 Location: Bakersfield, CA Posts: 308	Dual Electric Fans??? Should I switch to 7 Blade w Clutch? I'm about a month in on my new to me 70 gmc LWB 1/2t with 350/350. I think it was setup with a camper before (some weird wiring on the firewall and some "extra" wires going back to bed). ANyway, Previous owner put in dual electric fans (no flex or 7 blade fan on my engine). They also have the fans hooked up to a toggle switch??? I've only driven the truck off the trailer and onto the side of my house. I've ran the engine a few times since then to make sure it still starts. My questions are: 1. Shouldn't the fans be wired differently? I'm in Bakersfield, CA BAKERsfield! It will easily be over 100 degrees for like 60-90 days this summer. I need this thing to stay cool. 2. Should I just scrap the whole electric fan thing and get a 7 blade with clutch? If so, which specific one should I get for my 350? Don't care about "period correct" just want "works when it's hot outside". Hopefully not too expensive cause this is a budget build. 3. If I do put a 7 blade on, would there be any benefit to leaving the electric fans in? Sorta double dipping? Or are they just going to be in the way of eachother?? Thanks,

05-09-2018, 01:14 PM	#2
HO455 Post Whore Join Date: Feb 2016 Location: Portland Oregon Posts: 11,270	Re: Dual Electric Fans??? Should I switch to 7 Blade w Clutch? Most definitely can be wired differently. There are nice electronic controllers available to automatically operate your fans. Or if your budget is restricted there are good wrecking yard options. Before making a decision about which way to go what are your plans for the truck? Will you be in stop and go traffic? Electric fans are helpful in traffic hell. But not all electric fans are created equal. Some are up to the task of cooling a V8 others are not. Can you post some pictures of the current set up. Someone here will be able to help with determining if they will do the job. You are correct about the electric and mechanical fans interfering with each other with reduced air flow through the radiator. I believe that a Camper Special should have come with a four row radiator. Does yours have one? Welcome aboard and let me be the first to ask for pictures. __________________ Thanks to Bob and Jeanie and everyone else at Superior Performance for all their great help. RIP Bob Parks. 1967 Burban (the WMB),1988 S10 Blazer (the Stink10 II),1969 GTO (the Goat), 1970 Javelin, 1952 F2 Ford OHC six 4X4, 29 Model A, 72 Firebird (the DBP Bird). 85 Alfa Romeo If it breaks I didn't want it in the first place The WMB repair thread http://67-72chevytrucks.com/vboard/s...d.php?t=698377 Last edited by HO455; 05-09-2018 at 01:16 PM. Reason: -4 grammar

05-09-2018, 01:53 PM	#3
RustyBucket Registered User Join Date: Jul 2009 Location: Space Coast, Fl. Posts: 1,050	Re: Dual Electric Fans??? Should I switch to 7 Blade w Clutch? I vote for the 7 blade fan ...just my opinion. I have 7 blade clutch fans with shrouds on both of my trucks. '72 Blazer is a mild big block with fact. A/C and 4 core radiator. The '71 GMC is a mild 350 w/aftermarket A/C and an aftermarket aluminum radiator. It's HOT in central Florida and I have 160 deg. thermostats in both of them. The clutch fans run nice & quiet and cool very well. The fan blades and clutches aren't expensive and are available through chain parts stores. Good shroud makes a big difference. I'd take the electric fan off. __________________ Dad always said, "Son, WISH IN ONE HAND, and ......." -------------------------------------- -------------------------------------- Current toy trucks: '71 GMC 1500 SUPER CUSTOM short/step, orig. dk. blue, 350/700r, ps,pb, A/C '72 Blazer 2wd, ochre & white, 454, tremecTKO 500 5spd. ps, pb, A/C, tilt Last 10yrs of hobby vehicles, had a FEW more in the 50yrs. before these: '66 Plymouth Belvedere City of Miami cop car clone. '70 Nova 406"sb, 13.5-1, solid roller, Brodix, p.glide/t.brake, back halved, 9" Ford, spool 4.88, cage,ladder bar/coilover, 10.5 tire....... SOLD!! '67 C10 short/step side mount spare -- SOLD!! '72 Jimmy 2wd, 350/350, ps, pb, fun driver, lots of bondo & a shiny red paint job..... SOLD!! '69 Nova 350, 4spd, A/C, ps, p.b, ...SOLD!!

05-09-2018, 02:11 PM	#4
hotwls13 Registered User Join Date: Mar 2018 Location: Bakersfield, CA Posts: 308	Re: Dual Electric Fans??? Should I switch to 7 Blade w Clutch? Here are the only pics I have of radiator/fans. I can get some better ones tonight. No idea what kind of fans or radiator I have. Attached Images

05-09-2018, 02:40 PM	#5
outfield Registered User Join Date: Apr 2016 Location: Portland, Or Posts: 387	Re: Dual Electric Fans??? Should I switch to 7 Blade w Clutch? From the pictures it looks like you could have a HD 4 row radiator which is good. I have this radiator in my 69 K20, its stock, and with the 7 blade clutch fan and shroud it has always stayed cool, even on hot summer days and when hauling.

05-10-2018, 12:42 PM	#7
HO455 Post Whore Join Date: Feb 2016 Location: Portland Oregon Posts: 11,270	Re: Dual Electric Fans??? Should I switch to 7 Blade w Clutch? A four core could of been factory. Look down into the radiator fill and count the rows of tubes across the radiator. Here is a link to a bunch of cooling system information. The author is a little bias with his brand loyalty but overall lots of good information. http://www.pirate4x4.com/tech/billavista/Cooling/ __________________ Thanks to Bob and Jeanie and everyone else at Superior Performance for all their great help. RIP Bob Parks. 1967 Burban (the WMB),1988 S10 Blazer (the Stink10 II),1969 GTO (the Goat), 1970 Javelin, 1952 F2 Ford OHC six 4X4, 29 Model A, 72 Firebird (the DBP Bird). 85 Alfa Romeo If it breaks I didn't want it in the first place The WMB repair thread http://67-72chevytrucks.com/vboard/s...d.php?t=698377

05-09-2018, 02:48 PM	#8
hotwls13 Registered User Join Date: Mar 2018 Location: Bakersfield, CA Posts: 308	Re: Dual Electric Fans??? Should I switch to 7 Blade w Clutch? Any links to a replacement fan/clutch? My google skills are lacking today. Keep coming up with flex fans or 7 blades for 6cyl

05-09-2018, 03:40 PM	#9
kenr74 Registered User Join Date: Apr 2018 Location: NW, Oregon Posts: 51	Re: Dual Electric Fans??? Should I switch to 7 Blade w Clutch? I had dual electrics on my K2500 hauler and loved them. I wired them up with temperature controllers so they came on when needed. https://www.jegs.com/i/JEGS/555/5212...AaAleVEALw_wcB I had one come on just above my thermostat temp and then the second came on about 20 degrees higher. I had a toggle on one of them also just as a back up but never used it. My butt dyno said I picked up a little usable power but not sure how accurate it is.

05-09-2018, 05:25 PM	#11
Rufas Registered User Join Date: May 2016 Location: Fort Mohave, AZ Posts: 368	Re: Dual Electric Fans??? Should I switch to 7 Blade w Clutch? I vote for the fan/clutch setup. When I installed my 468 BBC I went with dual electric fans. Never could get the cooling I needed. Went back to the original fan shroud and a 7 blade fan with clutch. The fan/clutch moves much more air than the electric fans. I can place my hand just outside the grill and feel air being pulled into the radiator and that's without the fan clutch engaged. __________________ 1970 GMC 2500 700R Trans, RideTech 4 link rear suspension, air bagged on all four corners, factory upper/lower A-Arms, 2 inch drop spindles. 350 SBC 300hp Weiand Supercharger FiTech 30004 EFI

05-10-2018, 12:02 AM	#12
RichardJ Registered User Join Date: Apr 2010 Location: So Cal Posts: 1,458	Re: Dual Electric Fans??? Should I switch to 7 Blade w Clutch? Loose the old Tube & Fin Condenser and replace it with a Parallel Flow type condenser. With the V8, I'd go with the 7-Blade clutch fan, but add an electric pusher fan in front with temp controller. Many cry that pusher fans aren't any good, but that doesn't stop the car manufacturers, including GM from using them. My truck has the original 4-blade and no shroud. The fan on the right side is a pusher from a '89 Cad, connected to a 208* temp switch. The fan on the left is a '94 Cad with bigger screen shield to protect my fingers at the hood release. It runs all the time the Ac is ON, which is all the time. When I added the AC and made the mount for the new Condenser, I included the two fans at the same time as a just in case. With the 4-blade and the one pusher fan running, temps are consistent with temps before the AC. Attached Images __________________ '67 GMC 2500, 292, 4spd, AC

05-10-2018, 11:03 AM	#13
CUDA8U Registered User Join Date: Apr 2018 Location: EDMONTON Posts: 260	Re: Dual Electric Fans??? Should I switch to 7 Blade w Clutch? get a 4 core champion aluminum rad and add a flex a lite 180 black magic fan

05-10-2018, 01:05 PM	#14
brown7373 Registered User Join Date: May 2011 Location: Fort Pierce, FL Posts: 430	Re: Dual Electric Fans??? Should I switch to 7 Blade w Clutch? My 72 350/350 with factory air never gets above 180-185. I live in south Florida and have NEVER had an overheating problem with a shroud, 7 blade and a clutch. If you go electric, you may need to upgrade your electrical system (charging) as they suck a lot more current than you alternator was designed for. A friend had a 454 71 Vette that ALWAYS overheated with electric fans and he ALWAYS had a weak battery. And that was after a total pro restoration. And for me, I don't like to listen to the roar of the electric fans at idle or when first shut down.

05-10-2018, 05:15 PM	#15
clay68c10 Senior Member Join Date: Aug 2004 Location: Centennial, CO Posts: 2,979	Re: Dual Electric Fans??? Should I switch to 7 Blade w Clutch? You already own the fans that are on it, give them a shot. If they work, then set up a more elaborate trigger to switch them on. If they don't work, then go mechanical or hi-capacity electric. That said, I ran a Lincoln MK8 fan on a 454 w/ac when I lived in TX. Even in stop and go DFW traffic with the air blasting, the eng temp never went over 205. A properly set up e-fan on a 4-core radiator will keep it cool. __________________ ClusterTruck: 68 C10 Bought in 89, wrecked in 03. Slow low $ rebuild started '17. 6.0 & TKO http://67-72chevytrucks.com/vboard/s...d.php?t=788602 93 K1500 Short Step, 350, NV4500, EBL flash ECU. Vortec heads & roller cam someday... 05 Jeep Wrangler Unlimited. 3” lift & 6-speed 02 E320 the insurance total “free car” 13 Tahoe LTZ

05-10-2018, 06:17 PM	#17
Mollzyie Registered User Join Date: Aug 2016 Location: Miami fl Posts: 289	Re: Dual Electric Fans??? Should I switch to 7 Blade w Clutch? Question to u guys . Do people ditch the 7 blade fan for performance reasons ? As in like racing or 1/4 mile . Mine is long gone before I bought the truck . __________________ M.A.G.A.

05-10-2018, 07:51 PM	#19
franken Registered User Join Date: Jun 2013 Location: Somewhere Posts: 3,100	Re: Dual Electric Fans??? Should I switch to 7 Blade w Clutch? Maybe dumb observations, but later trucks switched to 5 blade fans. I'm guessing GM found the effectiveness was sufficient and less blades reduced drag. Make sure the fans are pulling air through the radiator, not pushing forward. I'd vote clutch fan for simplicity...



Register or Log In To remove these advertisements.

05-11-2018, 04:34 PM	#20
MARKDTN Registered User Join Date: Jan 2011 Location: Chattanooga, TN Posts: 2,159	Re: Dual Electric Fans??? Should I switch to 7 Blade w Clutch? I vote keep the electrics and do proper control. Lots of schemes to control dual fans. __________________ '83 K20-TPI '73 C10 '79 C10-ex-diesel(SOLD) '07 Tahoe(Son driving) '14 Suburban-DD '71 C10-current project

05-14-2018, 12:02 PM	#21
hotwls13 Registered User Join Date: Mar 2018 Location: Bakersfield, CA Posts: 308	Re: Dual Electric Fans??? Should I switch to 7 Blade w Clutch? I was able to snap a few pics Yesterday: ANyone know where I can get a cap for the overflow bottle? Is that a factory overflow? Attached Images

05-23-2018, 05:15 PM	#22
68 P.O.S. Registered User Join Date: Jan 2007 Location: Puyallup, WA Posts: 1,662	Re: Dual Electric Fans??? Should I switch to 7 Blade w Clutch? That's an aftermarket overflow bottle. These trucks didn't have a factory overflow, just a tube from the radiator to the ground. There was a dealer optioned overflow bottle. Some government trucks and whatnot could have them (same as the dealer option), but weren't available to the general public. Here's a link for some info and pics http://67-72chevytrucks.com/vboard/s...d.php?t=546610 __________________ 72 C10 lwb fleetside -stock 350/350 combo Last edited by 68 P.O.S.; 05-23-2018 at 05:21 PM.

05-23-2018, 06:29 PM	#23
Artofdeath Registered User Join Date: Jul 2017 Location: Sandusky, Ohio USA Posts: 104	Re: Dual Electric Fans??? Should I switch to 7 Blade w Clutch? This maybe a silly question but, are the fans pushing or pulling air? They should be pulling air towards the engine. If they are pushing air towards the front of the vehicle you could have a dead zone. Just curious...

05-30-2018, 09:43 AM	#25
Rick Bollinger Registered User Join Date: Mar 2018 Location: Colchester IL Posts: 297	Re: Dual Electric Fans??? Should I switch to 7 Blade w Clutch? My thought is set up right electric fans would be alright. But I would think that the fan mounted right on the radiator would only pull air where the fan is mounted. If it is a 10" dia fan there is only 10" of area being pulled through the radiator. If it was set back a couple of inches and set on a shroud of some sort then it would pull from the whole radiator. I had this same problem with my 68. P.O. Had it all messed up. Electric fan wired into the electric choke wire no shroud and didn't even run. I went with a LMC shroud and a 18" flex fan. It looks clean and moves lots of air. Whole set-up around $100.00

Register or Log In To remove these advertisements.