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Thread: Thermal Clutch Fan

  1. #1
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    Thermal Clutch Fan

    I have been an SDC member since 1985, and mostly a lurker here, off and on for several years. A person can learn a lot by listening, and that goes for reading too I suppose. However, I have not found much about clutch fans here, so I thought I'd bring it up.

    Several years ago I installed a 7 blade, GM, 19.5" thermal clutch fan on a 56 Golden Hawk (Packard engine) and really liked the results: quieter, more air when needed, less when not needed, less parasitic HP loss etc. It mainly involved replacing the Packard water pump flange with a GM flange; press off/press on, since both have the same inner diameter. I then used an GM pulley from a "short waterpump" in GM language, and the rest was pretty much a piece of cake.

    I like the GM set up so well on the 56J, that I've toyed with the idea of repeating it on our GT Hawk. I am aware its probably easy to install an Avanti style bimetal clutch fan, but I'd prefer thermal and more blades. I have already determined the Stude flange ID is same as Packard and GM, so it is probably do-able, but has anyone else done this already? If so, I'd be interested in details, part numbers, etc.. Otherwise, I will press on, and report back later.
    Thanks,
    Joe Hall

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    I found a 7 bladed fan off of a mid 70's 442. You are right, it is much quieter than the 6 bladed fan offered by our vendors.(sorry). Adaptation is minimal. Any cutting that needs to be done, can be done on the spacer. You have to cut part of the nub off of the spacer for it to fit on the clutch assy, but other than that, it fits right on. You have to use a spacer. I put in a stud assy on the waterpump to mount the fan assy, and you may have to trim the studs for clearance. But all in all, very easy to do. Pic enclosed.


    This pic was taken back when I had a 6 blade fan on the car. But the installation is the same.

  3. #3
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    for those of us without lathes, I would think that an already-modded spacer would be a great idea (hint, hint vendors.) I don't think there is enough clearance on non-C/K models to use permanently installed studs; I use a stud threaded into one of the holes for initial location, start the other three bolts, then remove the stud and install the fourth bolt.

    AFAIK there is no bolt on thermostatic clutch to fit with no modifications; the ones available as direct replacements simply reduce the fan RPM but provide no thermostatic effect.
    --
    55 Commander Starlight
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    Nate, you are right, there is not a thermostatic clutch that will fit without modifications. I happen to find a good machinest who took car of this for me, and basically told me not to come back. My stuff did not meet the volume requirements of his company. His specialty was aircraft specialty parts. Did great work. Also, IIRC, the thickness of the flange is different on the GM clutch, as opposed to the one used on the Avanti, and opposed to the one handled by our vendors.

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    Chuck I like your idea, but the ID of the Stude spacer's centering hole is .675"; this is .050" larger than the ID of the GM clutch centering hole. So, unless I am missing something here, one would have to remove ALL the spacer nub sticking out past the pulley, and obtain a flat surface. The studs/bolts would then be used to keep everything centered. You've done it this way, so obviously it worked. But I wonder if a .677" OD shaft, pressed into the .625" spacer, with about .5" sticking out the forward side, turned down to about .623" would not serve as a better centering device?
    Hope I have not confused you, as I almost confused myself in writing this.
    Joe H

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    I just took all of the parts to the machinest, who chucked it into a lathe, and walla, it fit. I am not real sure what he did, but it was minute'.

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    After measuring and doublechecking about a dozen times, I bought an 18.5", seven blade fan for a 1974-82 Corvette with AC today off FleaBay. The fan is new, and came with a used thermal clutch for $76, including shipping. I picked a Corvette clutch because it has a .750" pilot hole, versus .625" on most others. This size seems easier to make an adapter for. So will report back later as to how it goes.
    Joe H

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    Please let me know. I am always interested in cooling.......check the temp in Dallas today.

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    Wow! Those temps remind me of living in 29Palms, California in the 1980s-90s. About six months of the year it was seldom below 100, even at night, and often above 110 during the day. Back then I drove only Studes year round; did not need a winter rat like here in Kentucky. I converted AC on all our Studes while living there (2 GTs and a 56J). I had a desert radiator shop make a 5-core radiator for the 56J. With the OEM 3-core, the AC had to be shut off when outside temps went above 100 (just when you really needed the AC). The GTs did OK, but I ran six blade flex fans on the engines and 16" pusher fans on all of them.
    Yep, looking at those Dallas temps sure does bring back memories!
    Joe

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    Here is a thread from a few years ago on this topic. I am actually finally getting around to installing the Jag thermostatic fan using Dan Miller’s adapter. I already installed the adapter to work with a viscous clutch fan I already had and it worked out really well. I talked to him about a year ago and he still has some adapter kits he made up in ‘07. This is a pretty easy install. I will post pics of mine in the next week or so.

    https://forum.foobar.c...187#post252187
    Last edited by Dan White; 08-03-2011 at 10:42 PM.
    Dan White
    64 R1 GT
    64 R2 GT

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    Thanks for the link Dan. Excellent reading. The fan specs Dan M. mentioned are near identicle to a standard GM clutch that fits most V8 GMs except Corvette. I believe the main difference between Corvette and most other GM is the fan bolt pattern (bigger) and pilot hole. The Vette's pilot hole is .750" versus .625" on most other GMs. I also noticed many clutches (including the one Dan M. listed) come with a removable bushing that is a .625" hole installed, and a .750" if removed.
    Guess I am gonna learn more, soon. THe ebay seller sent me a note today the Corvette clutch & fan is in the mail.
    I agree six blade flex fans are effective. I've only used the metal ones, and everyone of them has been loud at say 2500 RPM and up.
    Joe

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    Well the viscous, thermal fan setuo arrived today. It took about two hours to install. I then took the car out for about a 40 mile test drive. It runs about the same temp as it did before with the metal, six blade flex fan. It seems to pull a little more air, which stands to reason, considering it is seven blades with 2.25" pitch, moved about 3' closer to the radiator. The six blade was a two inch pitch.
    It is also defiitely quieter at higher RPMs, i.e. I usually shift around 3000. Before, it was a lot nosier anytime above 2500.
    All in all I am happy with it.
    Joe H

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