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Clutch Fan Conversion

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Limey SE
76 Malibu
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Post by 76 Malibu Tue Nov 08, 2022 5:07 pm

I am doing some work on my engine over the winter, which includes installing a new water pump (I still have the original!) While I have things apart, I was thinking of converting my 4 blade direct drive fan to a clutch fan. I have a universal 18" clutch fan in my garage that is almost new, so all I'd need is to buy a clutch.

This is the fan I have: https://www.summitracing.com/parts/der-17918?seid=srese1&gclid=Cj0KCQiAmaibBhCAARIsAKUlaKQfatu-2sUOr1kP7i2irTuDcMYGKeh0_zdmoYoaa9AP9yj9Db4qYJYaArlZEALw_wcB

RockAuto shows that a Hayden 2705 was used on A/C cars.

https://www.rockauto.com/catalog/emailpagetofriend.php?nurl=%2Fen%2Fcatalog%2Fchevrolet%2C1976%2Cmalibu%2C5.7l%2B350cid%2Bv8%2C1054808%2Ccooling%2Bsystem%2Cradiator%2Bfan%2Bclutch%2C6812

Will this conversion work okay? Will I need anything else (other than some nuts and bolts) or am I missing something?
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Post by Limey SE Tue Nov 08, 2022 7:28 pm

I can take a Pic of my SBC clutch fan tomorrow outta shed if you think it would help ??

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Post by 76 Malibu Wed Nov 09, 2022 7:27 am

Sure that would be great. Can you also measure the fan diameter?
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Post by zucchi Wed Nov 09, 2022 11:04 am

If your goal is better cooling, please permit me to share some observations…

Let's start with how our fan clutches work:



As you likely know, clutch fans were installed on cars that came with A/C. I think the purpose is to allow the fan to kinda "freewheel" when cold then lock up when hot so as to increase airflow and cooling efficiency when needed. I've also heard it's to help the engine warm up faster by reducing the amount of airflow around the engine until is's warm enough for the thermostat to open AND the radiator is warm enough for air to heat up the clutch to engage. If that were the case, why are fan clutches only installed on A/C cars? I suspect the actual reason for the fan clutch was to reduce fan noise.

Since the fan clutch is a multi-piece assembly, it's subject to failure. Most of the failures I've seen have been that the clutch stops locking up. It may give some to no resistance but essentially it doesn't lock up. This type of failure will cause the engine to run hot and even overheat. Of all the different kinds of failures, this is the most benigne because as long as you're moving and/or the weather is cold, you can avoid permanent damage. The more severe failures involve a loosening of the bearings inside the clutch. This manifests itself in the form of a change in engine vibration. I've seen one failure where the bearings failed and the clutch jammed, the fan became slightly off center causing a wobble and wore the bearings in the water pump causing it to fail. The worst failure I'm aware of was a catastrophic failure of the clutch shaft such that the fan detached and went into the radiator.

I have a 1968 hearse on a Cadillac chassis that was not ordered with AC. As a non-A/C car, it came with a fixed fan and no shroud. Shortly after I acquired it in 1993, I noticed it ran hotter than I liked so I got a shroud from a 1968 Cadillac in a wrecking yard and installed it on my hearse. The clearance between the shroud and fan was about the same as on my Monte Carlo. Since then, the hearse has been running noticeably cooler.

The first time I replaced the fan clutch on my Monte Carlo was in 1987. I bought a replacement from Kragen (now O'Reilly Auto Parts) with a lifetime warranty. I've had to replace it about every 10-years since (or roughly 120,000 miles). Every time I open the hood, I check the fan for any wobble or looseness which would indicate failure in the fan clutch bearings. In contrast, since I installed the fan shroud on my Cadillac, the one-piece fan hasn't failed.

One additional observation — a friend of mine has a 1971 Cadillac where the previous owner replaced the clutched fan assembly with a direct-drive flex-fan; by the way, this car has factory A/C. By the time my friend got the car, it started running warmer so his mechanic's solution was to install push fans in front of the radiator (freakin' monkeys). I examined it and determined he would benefit from a radiator job. Took his radiator to a place that does radiators for commercial vehicles such as earth movers. They upgraded the small 3-row core to a high-flow 4-row core. While the radiator was out, we got rid of the pusher fans and the flex fan then installed the original clutched fan. Now, on the hottest days with the A/C on in bumper-to-bumper traffic, the engine temperature gauge barely goes over the 1/4 mark.

The take away is, if you're having cooling issues, I recommend you start by upgrading your radiator. If you don't have a fan shroud, get one. If you have one, check it for cracks and/or separations then repair if necessary. If you really like the idea of having a 7-blade fan, go ahead and install it.
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Post by Joe73 Wed Nov 09, 2022 11:36 am

I went with the recommendations in this "cooling 101" thread. If you have time, I'd read this thread. Its long but very informative. https://www.chevelles.com/threads/cooling-101-setup-that-keeps-old-school-bbc-sbc-motors-nice-cool.606465/

I used their (2) 1" row aluminum radiator, Hayden fan clutch (number is in the thread as well as reason for not using the heavier one) recommendations. Real simple setup, inexpensive, no electric stuff to wire and its keeping big horsepower big blocks cool in the summer. I used to be of the common thinking that more rows in a rad are better but when you think about it, theres less surface area contacting cooler air. And when you have more rows its harder for the fan to pull large volumes of air through hence the need for electric fans. If you have time, I'd read this thread. Its long but very informative. https://www.chevelles.com/threads/cooling-101-setup-that-keeps-old-school-bbc-sbc-motors-nice-cool.606465/
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Post by 76 Malibu Wed Nov 09, 2022 10:43 pm

Thanks for all the info guys. No overheating issues with my car. I have a 3 core high efficiency rad, and it never runs hot. I have that clutch fan sitting in my garage and figured it would be more efficient to run than the old direct drive fan. I thought while I was in working on the engine why not do the upgrade for the price of a fan clutch. I have done this on other cars in the past and it cuts back on the high rpm fan nose and makes the engine spin a little freer.

I just wanted to make sure the parts I selected above will work and that I am not forgetting anything.
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Post by Limey SE Wed Nov 09, 2022 11:03 pm

76 Malibu wrote:Sure that would be great. Can you also measure the fan diameter?

Will get it done tomorrow for you I had to replace the water pump on our 01 Ram today what fun that was

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Post by bracketchev1221 Fri Nov 11, 2022 10:28 am

I did the same swap on mine. Mine had a history of belt slipping and when I got the car, that was the first thing I did was put a clutch fan on it. I got the fan and clutch from Summit as you are doing.
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Post by 76 Malibu Sun Nov 13, 2022 1:59 pm

bracketchev1221 wrote:I did the same swap on mine.  Mine had a history of belt slipping and when I got the car, that was the first thing I did was put a clutch fan on it.  I got the fan and clutch from Summit as you are doing.  

Thanks, this very helpful. It's nice to hear first hand experience that it will work.
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Post by Limey SE Sun Nov 13, 2022 2:14 pm

76 Malibu wrote:
bracketchev1221 wrote:I did the same swap on mine.  Mine had a history of belt slipping and when I got the car, that was the first thing I did was put a clutch fan on it.  I got the fan and clutch from Summit as you are doing.  

Thanks, this very helpful. It's nice to hear first hand experience that it will work.

Sorry took so long Sir, Water pump debacles were slowing me down.........  First wrong Pump then get back to the store (my friend took it back) then they send the wrong belt 2.5 days down waiting for the right parts EVEN AFTER ORDERING THEM ONLINE for store Pickup They still Picked the wrong parts BOTH DAYS LOL   affraid lol! Thumbs up

Anyways heres the pics


Clutch Fan Conversion 31506610
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Clutch Fan Conversion 31531310

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one Wild NON original
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Post by 76 Malibu Sun Nov 13, 2022 2:20 pm

Thanks Anthony, very helpful.
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Post by markmastrangelo Tue Nov 15, 2022 2:01 am

I did the same conversion last winter on my 67 Grand Prix without A/C. I basically installed A/C cooling package. The car ran hot when I got it. Replaced the 2 row radiator with a new 3 row radiator. Replaced the 4 blade fixed metal fan (noisey) with a standard duty fan clutch and 19",7 blade GM fan ( much quieter). The car doesn't run hot anymore, cranks better hot, and is noticeably quieter.

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