Radiator fan

[72c20customcamper]

I’m looking to upgrade my 5blade to a 7 but I’m getting mixed messages about fitment. The bolt pattern is the same for where it attaches to the clutch fan but they all state that the 17 inch 7 blade fan won’t fit a 68 c10. The fan on my truck is over 17 inches and the shroud is 19 1/2 inches . In my mind the 17 should fit but actually be smaller than the stock 5 blade fan. Is that it smaller and won’t pull enough air ? Any insight from anyone who’s done the switch to a 7 blade fan .

[Stocker]

I am only aware of 18" fans, which is what my K20 has -- factory stock, original, 7-blade. My shroud opening is also 19 1/2".

FWIW, when my OEM heavy-duty fan clutch failed several years ago, I replaced it with a Hayden #2747 which is still working perfectly, with no overheating.

[72c20customcamper]

Maybe that’s my problem Thanks

Summit says this one doesn’t fit the truck but fits Chevelle’s and other cars with a clutch fan . Why wouldn’t it fit ? It’s 18 inches

[HO455]

The GM engineers designed the fans to fit the shrouds for effective cooling, while the bean counters wanted to save money. The result is different numbers of blades for different applications. All the different Chevrolet & GMC fan blades fit the same shroud exit hole and have the same water pump bolt pattern. They will have the same end of blade to shroud gap and all should be partly out of the shroud.

Much of the confusion comes from when fans from vehicles other than our trucks are installed on a 67-72 truck.

Removed my 4 bladed fan and installed a 7 bladed fan on my 67 Burban. No issues as it was a 72 C10 fan.

Photos to give you an idea on how it should fit.

[Stocker]

Originally Posted by 72c20customcamper

Summit says this one doesn’t fit the truck but fits Chevelle’s and other cars with a clutch fan . Why wouldn’t it fit ? It’s 18 inches

Summit shows that fan is correct for my '72 K20. It should be good for your C10, assuming it has a SBC.

[72c20customcamper]

Originally Posted by Stocker

Summit shows that fan is correct for my '72 K20. It should be good for your C10, assuming it has a SBC.

Pretty weird it says no for a c10 but yes for a 20 . Everything’s the same .
Yes it’s a SBC 383 stroker

[72c20customcamper]

Originally Posted by Stocker

Summit shows that fan is correct for my '72 K20. It should be good for your C10, assuming it has a SBC.

This is weird it says it doesn’t fit a c20 or a k20

[best view]

Same one in my jimmy and k20 just do it

[Stocker]

Originally Posted by 72c20customcamper

This is weird it says it doesn’t fit a c20 or a k20

Yes, it is weird! When I looked before, it showed OK -- looked it up again and it says no. I'd bet money they made a mistake on their website and it will fit just fine.

Only difference I can think of is if it was a big block, the fan is larger diameter -- 19.5" I believe.

[Steeveedee]

I saw a thread, but can't find it now. Stock was 18" for a BBC. AC or HD cooling increased that to 19". I have yet to find that thread again. Maybe someone posted it or knows where it is. My '70 truck had an 18" fan, and the clutch is (still) located about 1/2" from the radiator, so the fan was way forward of the proper place in the shroud. I bought a 19" fan from Summit and formed a circular fan shroud from 1/8th inch aluminum strap 1-1/4" wide to get the proper coupling between the fan and that shroud. This truck ran super hot, from new. (My FiL bought it). When we inherited it, I got after that heating problem. All the above was done, but it wasn't until I put in a high-flow thermostat that the remaining heating issue was finally resolved. Before that thermostat, it was OK, but still got up about 200º pulling hills. After that high flow thermostat, it's rock-solid on 180º going up hills. Just never mind the noise from that 2747 severe duty fan clutch.

[Stocker]

With all due respect, per Hayden's site, 2747 is heavy-duty, not severe-duty. Their site shows the differences between both of those and light-duty. My K20 has had a 2747 for years and is not noisy.... maybe it's a difference in fans bolted to the clutch?


EDIT: Different brand but appears to be the same specs, and it definitely shows it fits our trucks. https://www.classicindustries.com/pr...arts/k193.html

[72c20customcamper]

I’m going to order two . One for the 68 and the 72 . The 72 has the later style alt and pulleys and the fan is to far in the shroud because of the long water pump but I found that Hyden now makes a 2947 clutch fan which is much shorter than the 2747 . I ordered one from Rock Auto .

https://www.haydenauto.com/en/produc...ile-fan-clutch

[Steeveedee]

Originally Posted by Stocker

With all due respect, per Hayden's site, 2747 is heavy-duty, not severe-duty. Their site shows the differences between both of those and light-duty. My K20 has had a 2747 for years and is not noisy.... maybe it's a difference in fans bolted to the clutch?


EDIT: Different brand but appears to be the same specs, and it definitely shows it fits our trucks. https://www.classicindustries.com/pr...arts/k193.html

I don't know how I got that nomenclature wrong. Thanks for the correction!