Solid vs. clutch fan horsepower difference?

[hunt2elk]

Wondering if anybody has done any testing or read any articles about the horsepower gain by going to a clutch type fan over a solid one.
This is for my 69 RR. The car is a 383 w/22" radiator and a 223 fan with a 2" spacer. I had the radiator recored several years ago with a 3 core. Everything fit and worked fine. I just dropped in a new 451 and am trying to switch over to a clutch fan. I have a 215 fan, but am struggling to find a clutch that is short enough. The factory ones were 2.25" on this setup. So if I say screw it and use my original solid fan, what kind of power do you think I am leaving on the table?

 

[WileERobby]

Consider the Hayden short one ( I think its 2765)

 

[hunt2elk]

Consider the Hayden short one ( I think its 2765)

I think that one is a standard - non heavy duty unit designed for a Jaguar?

 

[lewtot184]

i think the biggest problem with something like the factory 7 blade steel fan is weight. there are much lighter fixed 6 blade fans out there. i don't have any heart burn with the flex fans; they're much lighter. there are aftermarket clutches being made now but they're over $200 to buy them. max engine rpm made be a consideration also.

 

[71airgrabberRR]

I'm pretty sure the Mopar Performance catalogue offers a package listed as a "viscous fan" unit and they say its good for 15 horsepower. I have never tried it out on a dyno to verify it though.

 

[Funship32]

Hunt2Elk: HP wise I've heard the same number as 71airgrabber offered up. Obviously that number may depend on RPM, etc. But still...not spinning a fan around is going to offer some HP gain. As for a fit, I was kinda in the same boat. I purchased off of Ebay a alum 7 bladed chry's unit that came with a TRW FC-28 clutch. The clutch was bad and any kind of supposed 'replacement' offered by the local boys wouldn't fit. Trying to find a TRW unit was cost prohibitive. Also read about the Jag unit but also wasn't impressed by the seemingly short life expectancy. So I basically downloaded the Hayden catalog, took some measurements and ended up getting a thermal clutch for a '69 AMX. Part number 2705. Overall length 3.11" which fit for me. For a comparison, the Jag clutch is 2.67". Hope that helps.

 

[hunt2elk]

Haven't been messing around with this lately as I just got my new third member put together and should have it installed this weekend. Then on to the fan clutch. I picked up a really nice original fan clutch from a buddy off a 69 A-body 340 car. It measures 2.75". I think this one may fit, but it will still be close.

 

[krowbar]

Could go with an electric fan.