Fan and Clutch Quandry

[The Rocknrod]

The only seven (7) blade 17" inch fan I can find is this one. Fan
To use it I need to use this fan clutch due to the bolt pattern. clutch - It's a Hayden 2711. Comes with a 5/8 - 3/4 bushing.
Which means I need to use a water pump with a 5/8 pilot. If I used a 3/4 pilot WP I'd have to get a corvette 2 groove ($$) plus they are smaller in diameter, not sure if thats a bad thing.
What do you think? The 6" Corvette Pulley (3/4" hole)? Vice the SBC water pump pulley of 6.4" Diameter?

[The Rocknrod]

Maybe I'll just go with a Derale 6 blade fan

And a Hayden 2797 Fan Clutch.

[geezer#99]

Speedway has a six blade.

https://www.speedwaymotors.com/Flex-...sku=9101575-17

[The Rocknrod]

Originally Posted by geezer#99

Speedway has a six blade.
https://www.speedwaymotors.com/Flex-...sku=9101575-17

Thank you. I'm primarily sticking with a "clutch Fan" though.
I had to re-read your link cause even Summit shows a Vintage Air 17" clutch fan as a direct drive unit. Although the description is clear it is a clutch fan. Checking with VA they show it is also.

[AcampoDave]

I used and 18" six blade and a Hayden 2747 heavy duty and it worked out great. When we hit those triple digit temps I can definitely hear it doing it's job. I run a small block, manual trans with a/c and and an aluminum radiator. The 18" fan just fits the stock shroud with about a finger width of clearance. I'm not crazy about the roar of the blades when it's hot, but I do love the simplicity of a mechanical fan. I'm sure a standard duty would be quieter but probsbly wouldn't be adequate for the a/c. I got both fan and clutch from my local O'Reilly auto parts

[The Rocknrod]

Originally Posted by AcampoDave

I used and 18" six blade and a Hayden 2747 heavy duty and it worked out great. When we hit those triple digit temps I can definitely hear it doing it's job. I run a small block, manual trans with a/c and and an aluminum radiator. The 18" fan just fits the stock shroud with about a finger width of clearance. I'm not crazy about the roar of the blades when it's hot, but I do love the simplicity of a mechanical fan. I'm sure a standard duty would be quieter but probsbly wouldn't be adequate for the a/c. I got both fan and clutch from my local O'Reilly auto parts

Oh good to know Dave, thanks. So with the SBC how far into the shroud does 2747 put the fan? The 2747 and 2797 are the same as far as fan mount height. Just the 2797 is a super duty instead of heavy duty.

[The Rocknrod]

Never mind Dave I found your previous post and pictures (great info) - http://67-72chevytrucks.com/vboard/s...50&postcount=5

[Captainfab]

The proper placement of a fan within the shroud will also depend on whether the correct short water pump is used or if the later model long water pump is used.

[The Rocknrod]

Originally Posted by Captainfab

The proper placement of a fan within the shroud will also depend on whether the correct short water pump is used or if the later model long water pump is used.

Good point Captainfab, here is the difference in length of the two Chevy small block pumps:

[rpmerf]

Here is what I have. 1970 C20 Custom Camper with a 350. I got the clutch from the junkyard out of an 80's Suburban. Here is the fan I used.
https://www.summitracing.com/parts/flx-5718/overview/ - 18", standard rotation.

Looks like they don't sell that one anymore, and this is the replacement.
https://www.summitracing.com/parts/flx-6718

Note they say 4000 RPM Max. The clutch should spin the fan about 80% of the engine speed, so you should be good to 5000 RPM.