correct fan blades? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

briank · 07-06-2013, 07:18 AM

Can someone help in what the factory correct fan blades are for 67-72 trucks. I have a 70 k5 that was a 307, now 350 2bbl that I have a 5 blade clutch fan that appears correct per the sales brochure for that year. I have a 72 k5 with a 350 4bbl, no a/c that I thought should have a 7 blade clutch fan but the brochure shows a 4 blade w/o a clutch fan. Can someone help out?
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**chiefcfd** · 07-06-2013, 09:09 AM

My 72 with 307 and no a/c had a 4 blade w/o a clutch. I think the a/c trucks had clutch fans but not for sure.

**Stocker** · 07-06-2013, 10:33 AM

It varies by engine, A/C or not, and probably by model year. My '72 with 350 and A/C still has the OEM 7-blade 18" clutch fan.

briank · 07-06-2013, 11:49 AM

Still confuses me. My 5 blade clutch fan came on a 307 non ac and Im guessing its original as eveything thing else was. Anybody else wanna chime in ?
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**FirstOwner69** · 07-06-2013, 12:19 PM

My 69 C/20 with A/C came new with a 5 blade clutch fan. Some time ago there was a for sale thread that got into this discussion. Someone there said all clutch fans on A/C trucks were 7 blade and on non A/C trucks were all 5 blade. All measured 18". BUT, as I said above mine has always been a 5 blade. I also recall reading that no A/C trucks used a clutch.

Probably just adds confusion and doesn't answer your question. I doubt there will be a consensus on this.

Jim

sc_frontier · 11-26-2013, 11:27 AM

my 70 c10 has a four blade clutch-LESS fan.
350, 4bbl, 3 speed manual, NO a/c, no powerbrakes, 3.08 rear, longbed.

Spartan · 11-26-2013, 12:13 PM

This is a good question. Which year with such and such an engine came from the factory with this fan/fan clutch set up.
Subd

**FirstOwner69** · 11-26-2013, 04:49 PM

Quote:

Originally Posted by FirstOwner69

My 69 C/20 with A/C came new with a 5 blade clutch fan. Some time ago there was a for sale thread that got into this discussion. Someone there said all clutch fans on A/C trucks were 7 blade and on non A/C trucks were all 5 blade. All measured 18". BUT, as I said above mine has always been a 5 blade. I also recall reading that no A/C trucks used a clutch.

Probably just adds confusion and doesn't answer your question. I doubt there will be a consensus on this.

Jim

To amend what I said in this post... Last sentence in first paragraph should say "I also recall reading that no non-A/C trucks used a clutch".

gvw5400 · 11-26-2013, 10:51 PM

Two trucks I know with 350's, 4 spd.,No a/c, both have 4 blade air chopper no clutch fans. A 70 and 71 C10's. The 71 has the HD cooling radiator(3 core).

**chiefcfd** · 11-28-2013, 12:07 AM

My 72 had 4 blade fan no clutch. 307 non a/c. 2row radiator.

Andy4639 · 11-28-2013, 08:14 AM

Here is mine on a 71 Chevy. I swapped everything off my stock 307 to the 305 TPI motor when I did the engine swap back in 1989.7 blades with clutch.

**Steeveedee** · 12-01-2013, 10:20 PM

Based on my experience, factory AC always gets a fan clutch. There may be rare exceptions. My '64 Impala had the SHP 300 HP 327, and it came with a fan clutch, even without AC. A fan clutch is a performance item, that may be why. Or it could be that the guy who bought it new walked down the assembly line while it was being built and made sure everybody did it right. I was the third owner, and my dad knew the first owner, is how I know. It ended up with SS spinner wheel covers, even though it wasn't an SS. Low options- SHP 327, close ratio 4-speed, 3.90 Posi, tach and a radio with rear seat speaker. He raced the living snot out of it. Boy, would I like to have that, now.

Spartan · 12-04-2013, 12:44 AM

I did a little research and found the answer. I went to the GM Heritage site and took a look in the archives. Basically typed in my model year and they have the data on PDF. MY truck is a 69 and like mentioned in an earlier post it depends on year/engine size/and options like A/C and Hd cooling.
So... for a K20 350 no A/C 4 blades x 18 inches dia. This scared me because mine has 5 blades...alas I went back to the chart and HD cooling is 5 blades x 18" dia. BUT wait there's more... same truck with HD radiator has 4 blades... which leads me to the question...does heavy duty cooling include a heavy duty radiator? They are listed in different rows so one could have one without the other...
So there's still a little mystery but you can find all your particular info at the GM Heritage website.
Hope this is helpful
Cheers!
Nim

69GMCLonghorn · 12-05-2013, 05:48 PM

Unless you're building a 100% stock rig, I wouldn't sweat which model came with what. After converting my last truck from a non-clutch to a clutch with a flex fan, that is the ONLY set up I will ever run again... And don't say it: I despise electric toy fans. No need if your cooling system is working right.

07-06-2013, 07:18 AM	#1
briank Registered User Join Date: Sep 2011 Location: Leland, Il Posts: 1,503	correct fan blades? Can someone help in what the factory correct fan blades are for 67-72 trucks. I have a 70 k5 that was a 307, now 350 2bbl that I have a 5 blade clutch fan that appears correct per the sales brochure for that year. I have a 72 k5 with a 350 4bbl, no a/c that I thought should have a 7 blade clutch fan but the brochure shows a 4 blade w/o a clutch fan. Can someone help out? Posted via Mobile Device

07-06-2013, 09:09 AM	#2
chiefcfd Senior Member Join Date: Oct 2010 Location: Cadiz, Ky Posts: 514	Re: correct fan blades? My 72 with 307 and no a/c had a 4 blade w/o a clutch. I think the a/c trucks had clutch fans but not for sure. __________________ 1972 Chevy LWB Roadster 1999 Chevy Silverado 2wd 2015 Chevy High Country 4x4 Crew Cab

07-06-2013, 10:33 AM	#3
Stocker 20' Daredevil (Ret) Join Date: May 2003 Location: Jefferson State Posts: 13,722	Re: correct fan blades? It varies by engine, A/C or not, and probably by model year. My '72 with 350 and A/C still has the OEM 7-blade 18" clutch fan. __________________ - Mike - 1972 K20 LWB 350/350/205 RIP El Jay

07-06-2013, 11:49 AM	#4
briank Registered User Join Date: Sep 2011 Location: Leland, Il Posts: 1,503	Re: correct fan blades? Still confuses me. My 5 blade clutch fan came on a 307 non ac and Im guessing its original as eveything thing else was. Anybody else wanna chime in ? Posted via Mobile Device

07-06-2013, 12:19 PM	#5
FirstOwner69 Senior Member Join Date: May 2010 Location: Wisconsin & Arizona Posts: 4,852	Re: correct fan blades? My 69 C/20 with A/C came new with a 5 blade clutch fan. Some time ago there was a for sale thread that got into this discussion. Someone there said all clutch fans on A/C trucks were 7 blade and on non A/C trucks were all 5 blade. All measured 18". BUT, as I said above mine has always been a 5 blade. I also recall reading that no A/C trucks used a clutch. Probably just adds confusion and doesn't answer your question. I doubt there will be a consensus on this. Jim

11-26-2013, 11:27 AM	#6
sc_frontier Registered User Join Date: Jul 2013 Location: Sherman, Tx Posts: 16	Re: correct fan blades? my 70 c10 has a four blade clutch-LESS fan. 350, 4bbl, 3 speed manual, NO a/c, no powerbrakes, 3.08 rear, longbed. __________________ SC

11-26-2013, 12:13 PM	#7
Spartan Registered User Join Date: Dec 2012 Location: Backwoods, OR Posts: 888	Re: correct fan blades? This is a good question. Which year with such and such an engine came from the factory with this fan/fan clutch set up. Subd __________________ '69 K20 350/4 speed/Rockwell/D44/HO52. "orange rhymes with door hinge"

11-26-2013, 10:51 PM	#9
gvw5400 Registered User Join Date: May 2013 Location: Colorado Rocky Mountains Posts: 263	Re: correct fan blades? Two trucks I know with 350's, 4 spd.,No a/c, both have 4 blade air chopper no clutch fans. A 70 and 71 C10's. The 71 has the HD cooling radiator(3 core).

11-28-2013, 12:07 AM	#10
chiefcfd Senior Member Join Date: Oct 2010 Location: Cadiz, Ky Posts: 514	Re: correct fan blades? My 72 had 4 blade fan no clutch. 307 non a/c. 2row radiator. __________________ 1972 Chevy LWB Roadster 1999 Chevy Silverado 2wd 2015 Chevy High Country 4x4 Crew Cab

11-28-2013, 08:14 AM	#11
Andy4639 Old member Join Date: Jan 2002 Location: Liberty, & Garden City S.C. , U.S. Posts: 19,945	Re: correct fan blades? Here is mine on a 71 Chevy. I swapped everything off my stock 307 to the 305 TPI motor when I did the engine swap back in 1989.7 blades with clutch. __________________ 1971 LWB Custom, 6.0LS & 4L80E, Speedhut.com GPS speedometer & gauges with A/C. 20" Boss 338's Grey wheels 4 wheel disc brakes. My Driver Seeing the USA in a 71 Upstate SC GM Truck Club 2013,14 and 2016 Hot Rod Pour Tour http://upstategmtrucks.com/ Get out and drive the truck this summer and have some fun! It sucks not being able to hear! LWB trucks rule, if you don't think so measure your SWB! After talking to tech support at Air Lift I have found out that the kit I need is 60811. Per the measurements I gave them. Ride height of truck inside spring and inside diameter of springs.

12-01-2013, 10:20 PM	#12
Steeveedee Who Changed This? Join Date: Jan 2013 Location: Simi Valley, CA Posts: 10,676	Re: correct fan blades? Based on my experience, factory AC always gets a fan clutch. There may be rare exceptions. My '64 Impala had the SHP 300 HP 327, and it came with a fan clutch, even without AC. A fan clutch is a performance item, that may be why. Or it could be that the guy who bought it new walked down the assembly line while it was being built and made sure everybody did it right. I was the third owner, and my dad knew the first owner, is how I know. It ended up with SS spinner wheel covers, even though it wasn't an SS. Low options- SHP 327, close ratio 4-speed, 3.90 Posi, tach and a radio with rear seat speaker. He raced the living snot out of it. Boy, would I like to have that, now. __________________ ~Steven '70 Chevy 3/4T Longhorn CST 402/400/3.56 Custom Camper Simi Valley, CA

12-04-2013, 12:44 AM	#13
Spartan Registered User Join Date: Dec 2012 Location: Backwoods, OR Posts: 888	Re: correct fan blades? I did a little research and found the answer. I went to the GM Heritage site and took a look in the archives. Basically typed in my model year and they have the data on PDF. MY truck is a 69 and like mentioned in an earlier post it depends on year/engine size/and options like A/C and Hd cooling. So... for a K20 350 no A/C 4 blades x 18 inches dia. This scared me because mine has 5 blades...alas I went back to the chart and HD cooling is 5 blades x 18" dia. BUT wait there's more... same truck with HD radiator has 4 blades... which leads me to the question...does heavy duty cooling include a heavy duty radiator? They are listed in different rows so one could have one without the other... So there's still a little mystery but you can find all your particular info at the GM Heritage website. Hope this is helpful Cheers! Nim __________________ '69 K20 350/4 speed/Rockwell/D44/HO52. "orange rhymes with door hinge"

12-05-2013, 05:48 PM	#14
69GMCLonghorn Registered User Join Date: Dec 2006 Location: Porter Ranch, CA Posts: 978	Re: correct fan blades? Unless you're building a 100% stock rig, I wouldn't sweat which model came with what. After converting my last truck from a non-clutch to a clutch with a flex fan, that is the ONLY set up I will ever run again... And don't say it: I despise electric toy fans. No need if your cooling system is working right.



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