Fan clutch options

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daves66valiant

daves66valiant

68 Dart 340/727:66 Signet Vert 340/5spd: 68 D100
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So I’m not running A/C and I believe what I have here is a factory original thermal fan clutch for an A/C car since it has the spring thingy. Not sure if this is a good functioning clutch yet and don’t want to find out necessarily. Would rather just replace it at this point in my build. Although it does not spin easily it does spin. I curious as to how these things would fail actually.

Any good purchasing opinions/options for an OEM viscous/torque style fan clutch?


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I am running this on my 69 Dart. It should have some tension when turning. When they fail the blades will spin freely, it will overheat and now cool down.
 
Hayden now has a "short shaft" clutch fan offered that works well. This is thanks to the work of many here on FABO. I'll try to post the part # tomorrow, unless someone knows it off hand?
 
str12-340 said:
Hayden now has a "short shaft" clutch fan offered that works well. This is thanks to the work of many here on FABO. I'll try to post the part # tomorrow, unless someone knows it off hand?
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I would love the part number. Thanks
 
Here's two of the shorter options, next to the MP fan and clutch.
But with an original engine and fan, may not need those. Clearence is only a problem when modifications have been made, in particular using the longer nosed later water pumps.
PS. If you go aftermarket, check all dimensions, not just overall ht. Such as water pump to fan attachment, diameter of center and bolt circle, etc.
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daves66valiant said:
Although it does not spin easily it does spin.
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That's how it works. Yours is both speed and temperature dependent.
daves66valiant said:
I curious as to how these things would fail actually.
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My personal experience has been failure when worn - they get sloppy and wobble.
However, regardless of make, sometimes they will fail when fluid drains out or similar and spin freely as Steven posted.
 
Mattax said:
Here's two of the shorter options, next to the MP fan and clutch.
But with an original engine and fan, may not need those. Clearence is only a problem when modifications have been made, in particular using the longer nosed later water pumps.
PS. If you go aftermarket, check all dimensions, not just overall ht. Such as water pump to fan attachment, diameter of center and bolt circle, etc.
View attachment 1715267882
Click to expand...

I have a new short one like in the pic setting on the shelf , only 2 5/8" tall. Also have the long orig morpar clutch too.
 
I researched the crap out of Hayden heavy duty thermal clutch fans and found a Cadillac application (Hayden 2731 or 4 Seasons 36999) had the best fit with regard to depth in the shroud on a stock 3 core radiator, cast iron pump in a '69 Dart 340. The "correct" listed fan clutch 2707 and 2747 did not have the correct depth in the shroud.
 
so the longer shaft unit put the fan so close to the stock radiator in my 1970 Dart that I had to take the radiator out to get the fan and water pump off - no its not supposed to be that way. This was true for both the old unit that Hayden sold for the application and the MP unit that came with a fan. I have 2 original fan clutches from 1970 Darts with AC and the heavy duty radiator and the Hayden 2947 is the closest to the original from the mount surface where it mates with the water pump to the face of the unit. I have them on two small block Darts with no cooling issues.

Remember that the fan clutch has to fit on the water pump center shaft snugly - if there is slop you can't precisely get the fan centered leading to an off balance clutch and fan that will quickly eat the water pump bearing and seal.
 
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