#1  
Old 06-27-2020, 09:17 PM
pngoat pngoat is offline
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Default Hayden 2747 & 2797 fan clutches

Does anyone know at what temperature the Hayden 2747 & 2797 fan clutches activate? the 2747 is listed as heavy duty & the 2797 is listed as severe duty. The activation temperature is not listed for either one. Stock cooling system, with shroud, on a 65 GTO 389. Any help appreciated. Thank You.

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Old 06-28-2020, 10:57 AM
mgarblik mgarblik is online now
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I am in the process of heavily researching a fan clutch for a custom application. (62 Catalina) I have found that if you Google Hayden Fan clutch catalog, you can download a 2010 catalog that is easy to print pages and compare specs and dimensions. That's the newest I could find that was easy to work with and print. There is about 15 pages of dimensions and performance info in that catalog. If you don't want to go into that much detail here are some generic specs. The fan clutches you mentioned will begin to clutch at approximately 170 degrees AIR temperature, which would be around 200-205 water temp. The HD 2747 clutch will spin at about 25-35% shaft speed disengaged and 70-90% shaft speed fully engaged. Designed to be used with a fan pitch less than 2". The severe duty 2797 clutch is deeper and heavier. Same engagement temp. 20-30% shaft speed disengaged, 80-90% engaged. Designed for fans with more pitch. Bottom line if you have room for the severe duty clutch without hitting the radiator, it will run a little faster hot and drive a more aggressive fan blade pitch. In either case, the engagement temp is too high for an old muscle car and the thermal spring can be modified to lower the engagement temp 15-20 degrees easily by carefully lifting the spring carefully from it's outer anchor point and twisting it clockwise and letting it rest against the outside of the stop. (not in the slot as OE). This makes them work much better in an old muscle car that you want to run around 180-185 degrees. Hope this helps.

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Old 06-28-2020, 12:02 PM
pngoat pngoat is offline
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Very helpful information. Thank you.

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Old 06-29-2020, 09:57 AM
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Quote:
Originally Posted by mgarblik View Post
I am in the process of heavily researching a fan clutch for a custom application. (62 Catalina) I have found that if you Google Hayden Fan clutch catalog, you can download a 2010 catalog that is easy to print pages and compare specs and dimensions. That's the newest I could find that was easy to work with and print. There is about 15 pages of dimensions and performance info in that catalog. If you don't want to go into that much detail here are some generic specs. The fan clutches you mentioned will begin to clutch at approximately 170 degrees AIR temperature, which would be around 200-205 water temp. The HD 2747 clutch will spin at about 25-35% shaft speed disengaged and 70-90% shaft speed fully engaged. Designed to be used with a fan pitch less than 2". The severe duty 2797 clutch is deeper and heavier. Same engagement temp. 20-30% shaft speed disengaged, 80-90% engaged. Designed for fans with more pitch. Bottom line if you have room for the severe duty clutch without hitting the radiator, it will run a little faster hot and drive a more aggressive fan blade pitch. In either case, the engagement temp is too high for an old muscle car and the thermal spring can be modified to lower the engagement temp 15-20 degrees easily by carefully lifting the spring carefully from it's outer anchor point and twisting it clockwise and letting it rest against the outside of the stop. (not in the slot as OE). This makes them work much better in an old muscle car that you want to run around 180-185 degrees. Hope this helps.
Can you take a picture of that or describe in more detail? It sounds like you are saying you detach the outer anchor point and let it go where it goes?

Thanks, Tony

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1967 Firechicken, 461, Edl heads, 262/266@0.050" duration and 0.627"/0.643 lift SR cam, 3.90 gear, 28" tire, 3520#. 10.01@134.3 mph with a 1.45 60'. Still WAY under the rollbar rule.
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Old 06-29-2020, 09:55 PM
mgarblik mgarblik is online now
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I have an article that describes the process. I don't have a clutch handy to take a pic of. Here is the link. Good information.

http://midamericachevelles.com/tech/...tch_adjust.pdf

Another way of thinking of this is you are pre-loading the bi-metallic spring making it "think" it is hotter than it actually is , engaging the clutch earlier.


Last edited by mgarblik; 06-29-2020 at 10:01 PM.
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Old 07-01-2020, 09:24 AM
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I read the article and it looks like you rotate the coil in the direction of tightening it to the next slot, it's that true?

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Old 07-01-2020, 09:58 AM
mgarblik mgarblik is online now
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Mostly. You are correct in that you tighten it in the direction that the spring is coiled, pre-loading it. But many of the fan clutches do not have a second slot to put the end into. So you can do one of two things. Carefully cut a new slot near the end of the bracket or just let the spring tang rest against the end of the bracket. It won't go anywhere because you tightened it by rotating it. It will just get tighter as it heats up. I have limited real world experience with this but plan to experiment myself in the near future. It all makes sense. Heavy duty truck clutches are adjustable from the factory.

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Old 07-03-2020, 11:29 AM
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I have a Hayden 2797 and it has a second slot. I was running it with a factory 7 blade AC fan in my ,72 LeMans with a 9:1 455, stock 3 core radiator and a 160 F Tstat. The car would creap up to 200 idling in traffic. I replaced that set-up with a 7 blade flex fan and the car would only get up to 175 on a 90 F day in any driving, highway or traffic. I changed the Tstat to a 180 F and it doesn't get much warmer, up to 180 on a 90 F day after running on the highway.

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1967 Firechicken, 461, Edl heads, 262/266@0.050" duration and 0.627"/0.643 lift SR cam, 3.90 gear, 28" tire, 3520#. 10.01@134.3 mph with a 1.45 60'. Still WAY under the rollbar rule.
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Old 07-04-2020, 01:55 PM
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Quote:
Originally Posted by AG View Post
I have a Hayden 2797 and it has a second slot. I was running it with a factory 7 blade AC fan in my ,72 LeMans with a 9:1 455, stock 3 core radiator and a 160 F Tstat. The car would creap up to 200 idling in traffic. I replaced that set-up with a 7 blade flex fan and the car would only get up to 175 on a 90 F day in any driving, highway or traffic. I changed the Tstat to a 180 F and it doesn't get much warmer, up to 180 on a 90 F day after running on the highway.
Just to clarify, you removed the 2797 clutch and went with a direct drive 7-blade fan? Or did you add the flex style fan blade to the clutch? If direct drive, how noisy is the fan at highway speed?

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Old 07-04-2020, 08:40 PM
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I removed the clutch and factory 7 blade fan and replaced it with a 7 blade direct drive flex fan. Not noisy at all on the highway, or down the track. Put the same set-up in my brothers car with 530 Hp and a 3 core radiator and it runs the same temp.

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1967 Firechicken, 461, Edl heads, 262/266@0.050" duration and 0.627"/0.643 lift SR cam, 3.90 gear, 28" tire, 3520#. 10.01@134.3 mph with a 1.45 60'. Still WAY under the rollbar rule.
  #11  
Old 07-04-2020, 09:15 PM
mgarblik mgarblik is online now
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That's interesting. I may go the flex fan route if this clutch set-up I am trying doesn't pan out. Originally had the 4 blade direct drive OE fan and no shroud. Now have a factory shroud for AC cars and this clutch fan deal I am trying. Mind sharing the brand and diameter of the flex fan?

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Old Yesterday, 12:00 PM
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Quote:
Originally Posted by AG View Post
I have a Hayden 2797 and it has a second slot. I was running it with a factory 7 blade AC fan in my ,72 LeMans with a 9:1 455, stock 3 core radiator and a 160 F Tstat. The car would creap up to 200 idling in traffic. I replaced that set-up with a 7 blade flex fan and the car would only get up to 175 on a 90 F day in any driving, highway or traffic. I changed the Tstat to a 180 F and it doesn't get much warmer, up to 180 on a 90 F day after running on the highway.
Did you try adjusting the spring on the clutch?

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Old Yesterday, 04:36 PM
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Last winter I had to replace my aluminum radiator. Went
With a ColdCase with two rows of 1.25 tubes. Noticed my
Fan clutch had some wobble and installed original 5 blade
Power flex mechanical fan. Used a 160 superstat I had as
A spare to see how cool she would run. Well she stays at
165 around town and hits 170 on freeway after a few miles.
Once off freeway she goes back to 165! Well I admit the factory
fan has some noise only when getting up to highway speeds but
Quiets down right after. Like the blades flatten once up to speed.
Not planning on reinstalling fanclutch just yet, itís garage art.
Glad I hung the factory fine on the wall years ago.
I will say the Hayden clutch and 7 blade fan helped immeknsely
When I had original 3 core radiator.
Gerry.

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Old Yesterday, 09:46 PM
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Quote:
Originally Posted by 70GS455 View Post
Did you try adjusting the spring on the clutch?

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No, I doubt I will ever run it since I have a cold running motor problem using the 7 blade flex fan. I might try it just for a test if I ever get bored.

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1967 Firechicken, 461, Edl heads, 262/266@0.050" duration and 0.627"/0.643 lift SR cam, 3.90 gear, 28" tire, 3520#. 10.01@134.3 mph with a 1.45 60'. Still WAY under the rollbar rule.
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