Adjusting a Fan Clutch - Chevelle Tech
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post #1 of 18 (permalink) Old Aug 4th, 12, 9:16 PM Thread Starter
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Levon
 
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Adjusting a Fan Clutch

Many of us have/had overheating problems. Well I discovered an issue with Fan Clutches and that is that many are set to lock up after 210 deg. Early ones locked up much sooner. A simple adjustment on some result in them locking up at 170 or so deg. I did mine this AM and it dropped the engine temp to a stable 175 with a 160 stat in 75 deg temps.
Dean helped and posted the PDF article here:

Adjust fan clutch

Hope it might help some who are struggling with temp creep.

Levon Hovagimian
Team Chevelle #279
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Current Engine VortecPro 460 (513 HP) Original is resting
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post #2 of 18 (permalink) Old Aug 5th, 12, 12:25 PM
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Re: Adjusting a Fan Clutch

Quote:
Originally Posted by LevonH View Post
Many of us have/had overheating problems. Well I discovered an issue with Fan Clutches and that is that many are set to lock up after 210 deg. Early ones locked up much sooner. A simple adjustment on some result in them locking up at 170 or so deg. I did mine this AM and it dropped the engine temp to a stable 175 with a 160 stat in 75 deg temps.
Dean helped and posted the PDF article here:

Adjust fan clutch

Hope it might help some who are struggling with temp creep.
==================

Is your 175 deg with temp sender in the head!

If so thats very good!

But if the temp senders in the intake then be aware the 175 deg intake temp = approx 190-195deg in head temp in warmer summer temps and if thats a cruise temp then when you hit moderate traffic your motor will see 200-205+ deg .

Just to clarify something here, the HD fan clutch /HD Hayden thermostatic 2747 I rec using on 69-72 chevelles isnt set to lock up at the higher 210 deg mark you mentioned. It locks up at a much cooler temp than that and doesn't need any tweaking unless your motor needs more cooling then the HD fan clutch provides with its thermostatic spring in stock factory position as recieved from Hayden.

The Hd fan clutches generally lock up a bit tighter for more fan rpm = more air being pulled thru the rad and they also should be set to lock up at a slightly lower temp too both of which is why the HD thermal fan clutch I rec cools significantly better then the std thermal fan clutch that came on these cars.

But this is great info to know if someone used a fan clutch thats meant for newer app on a chevelle or if their fan clutches lock up temp was adj too high from factory so you can tweak it to lock up at a lower temp.

Thanks for posting it!!!!

BTW,since we are talking cooling my mild perf bbc in my 69 in 90+ deg outside temps (runs cooler in 75 deg outside temps!) with temp sender in head runs 178ish at cruise & 180-185 sitting in moderate stop/go trafffic never hitting 190 deg .

I get those great engine temps in hot 90+ weather with temp sender in head using a basically stock GM clutch fan cooling system setup (that i tweak to run cooler esp in hot 90+ deg temps) is a std flow 160 stat w-bypass drilled (vs stock 195 or 180)/hayden hd fan clutch (vs less effective stock std duty fan clutch)/stock gm 772 clutch fan and matching stock fan shroud/stock type 4 row rad(vs 2-3 core rad with less cooling efficnecy)/milodon stock repl hi flow pump (vs stock pump likely running newer less effective stamped steel impeller)/ 30% anti frz-70%dist water coolant mix(better heat transfer)/and of course also proper tuning of motor when it comes to timing(esp base with aftermarket non gm perf cam!)-proper fuel calibration in carb & running vac adv on full int vacuum for additonal timing at idle .

The 4 row rad/hi flow pump/hd therm fan clutch/std flow 160 stat/30-70 coolant mix/vac adv on full int vac & proper engine tuning COLLECTIVELY reduced overall stabilized cooling system-engine temps a lot as compaired to the stock gm clutch fan setup.

I have found this cooling system setup to consistantly be the key to reducing engine temps in hot weather they are a stock bbc or sbc to a pretty hot 496-502-540cid /550-600+hp bbc . This simple fairly inexpensive yet reliable effective cooling system setup satisfies them all from my many yrs of 1st hand exp dealing with & correcting running hot issues on stock for fairly hot street muscle cars running old school 35-40 yr old bbc/sbc motors these cars came with & not newer efi/ emmissions motors that are a diff story!

Scott

SCOTT
1969 CHEVELLE SS396,ORIGINAL #'S MATCH,GOT IN 1978,(In 2001 rblt/bored original 396 .030 to 402)/M20/12BOLT/3:31'S
2002 MAXIMA (DAILY DRIVER/1 owner,GOT 3/2013 w-44k miles)
2009 HD ELECTRAGLIDE CLASSIC ULTRA (GOT 11/14 W-9,700 miles)

Last edited by SWHEATON; Aug 5th, 12 at 5:43 PM.
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post #3 of 18 (permalink) Old Aug 5th, 12, 4:25 PM Thread Starter
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Levon
 
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Re: Adjusting a Fan Clutch

Anyone that has a fan clutch can check there's to see if the adjustment is available to them. The OLD Hayden we had here had it so it MAY be available on others???

Levon Hovagimian
Team Chevelle #279
70 Chevelle SS 454 LS5 4 speed.
Current Engine VortecPro 460 (513 HP) Original is resting
1966 427 Corvette SOLD
1973 Camaro IHRA Hot Rod (LS-6 Auto)11.00 @121 (Chased a 10.99 or better) SOLD

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post #4 of 18 (permalink) Old Oct 13th, 12, 12:43 PM
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Re: Adjusting a Fan Clutch

I just purchased the NAPA 2710 fan clutch for the short pump. I found a few threads on this adjustment and Im trying it this morning but I'm not sure how it will work. When I readjust the spring- counterclockwise- the valve it pivots around also spins. If I go clockwise- the tension also turns the pivot. Is this going to make a difference in this model of clutch. It seems like the tension on the spring is exactly the same as the center point pivots too? Hope i'm wrong but logic tells me otherwise... I see in other threads the counterclockwise turn is the way to adjust. Thanks Rob
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post #5 of 18 (permalink) Old Nov 6th, 12, 6:55 PM
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Re: Adjusting a Fan Clutch

I would listen to Scott, he seems to be very intune with cooling issues. I'm halfway there with his rec. New gauge in the head, new Hayden 2747 fan clutch, sealed shroud with foam tape*** new thermo still to be installed and 30-70% coolant mix.
NSF
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post #6 of 18 (permalink) Old Nov 7th, 12, 1:16 PM
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Re: Adjusting a Fan Clutch

Quote:
Originally Posted by Not So Fast View Post
I would listen to Scott, he seems to be very intune with cooling issues. I'm halfway there with his rec. New gauge in the head, new Hayden 2747 fan clutch, sealed shroud with foam tape*** new thermo still to be installed and 30-70% coolant mix.
NSF
Absolutely correct. Ours never exceeds 190 in 110+degree weather with the A/C on...I used Scotts ideas on our 71 LS5 utilizing a complete factory 98' BBC Burb serp belt system.

Marc S
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post #7 of 18 (permalink) Old Nov 7th, 12, 2:40 PM Thread Starter
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Levon
 
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Re: Adjusting a Fan Clutch

Quote:
Originally Posted by RHinkel764 View Post
I just purchased the NAPA 2710 fan clutch for the short pump. I found a few threads on this adjustment and Im trying it this morning but I'm not sure how it will work. When I readjust the spring- counterclockwise- the valve it pivots around also spins. If I go clockwise- the tension also turns the pivot. Is this going to make a difference in this model of clutch. It seems like the tension on the spring is exactly the same as the center point pivots too? Hope i'm wrong but logic tells me otherwise... I see in other threads the counterclockwise turn is the way to adjust. Thanks Rob
Hi Rob. Turning the spring is supposed to turn the "valve" The valve controls the lock up temp. Tension will be the same in either location.

Levon Hovagimian
Team Chevelle #279
70 Chevelle SS 454 LS5 4 speed.
Current Engine VortecPro 460 (513 HP) Original is resting
1966 427 Corvette SOLD
1973 Camaro IHRA Hot Rod (LS-6 Auto)11.00 @121 (Chased a 10.99 or better) SOLD

Priddis, Ab. Canada

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post #8 of 18 (permalink) Old Jan 5th, 13, 4:20 PM
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Bobby
 
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Re: Adjusting a Fan Clutch

One other thing Scott mentioned was the difference between sender in head VS intake, as I have both now there seems to be about 15-20 degrees separation
NSF
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post #9 of 18 (permalink) Old May 18th, 15, 8:56 AM
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Re: Adjusting a Fan Clutch

anyone try this on a the Hayden HD?
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post #10 of 18 (permalink) Old Jun 7th, 15, 6:31 PM
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Mike
 
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Re: Adjusting a Fan Clutch

For those driving 64 to 67 Chevelles. The Hayden 2747 can be used with early Chevelles but you will need to change your fan as the bolt pattern on this fan clutch (2747)will not fit your stock 17.5/ 18" fan. You can use the Hayden 6 blade fan 3618. This is a 6 blade fan with both 3" and 3.5" bolt patterns. the 2747 from the mounting surface to the water pump pulley to the blade mounting surface is only .17 inches or Aprox. 1/8" difference in length. I have a 67 with a 496 complete with Air, Power steering, Brakes Etc. and headers so the engine compartment is very full. Today it was on the north side of 85 degrees out and my temp never went above 180. This was in traffic!

There is no need to teak the new style 2747. See below. Hope this helps!

Thanks to S Wheaton (Scott) for some invaluable cooling tips!

Standard Duty Thermal (Stock 2710)
  1. Turns fan 60-70% of shaft speed when engaged
  2. Disengage to 20-30% of the shaft speed
  3. Used with lighter pitch fans. (1-1/2" of pitch)
  4. Flat plate impeller design with up to 11.4 Sq. In. of working surface
  5. Identified by a smooth steel faceplate & thermal spring assembly on the front side
Heavy-Duty Thermal (2747)
  1. Turns the fan 70-90% of the shaft speed when engaged for increased cooling
  2. Turns the fan 25-35% of the shaft speed when disengaged
  3. Used with deeper pitch fans. (2-1/2" of pitch)
  4. Land and groove design with up to 27 Sq. In. of working surface
  5. Identified by finned aluminum faceplate and thermal spring on the front

Mike
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post #11 of 18 (permalink) Old Jun 7th, 15, 8:50 PM
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Re: Adjusting a Fan Clutch

I would just get the HD clutch. Think I paid 150 for the clutch and fan was money well spent. I'm sure modifying the standard clutch works but you can damage it permanently or can fail prematurity. I would think there's a reason the HD clutch has cooling fins.
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post #12 of 18 (permalink) Old Jun 9th, 15, 10:06 AM
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Re: Adjusting a Fan Clutch

Keep something in mind when using thermal clutch fans, unless they are within 1-1/2" of the radiator, they will not operate per factory specs. The temperature at which they engage will be DELAYED!
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post #13 of 18 (permalink) Old Jul 31st, 15, 3:57 PM
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Re: Adjusting a Fan Clutch

Is the parasitic drag that substantial when using a newer type flex fan with no clutch, vs. a factory clutch fan setup? I realize the flex fan will always be spinning (and cooling too), but does it really rob the engine of that much power? (to be noticeable by the seat of your pants that is). And forget fuel economy. These cars are not meant to include that in the equation anyway.

Just wondering….
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post #14 of 18 (permalink) Old Aug 1st, 15, 1:31 PM
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Re: Adjusting a Fan Clutch

Probably a dumb question, but I'll ask it anyway.

After cruising and the engine getting to operating temp. for a while, if you shut the car off, should you be able to spin the clutch fan freely? Or should you not be able to spin it?

I would think, since the engine is hot, the clutch fan will be engaged, even with the engine off, therefore not making it possible to spin with your hands.

Just want to be sure I have this correct.
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post #15 of 18 (permalink) Old Aug 1st, 15, 1:45 PM Thread Starter
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Levon
 
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Re: Adjusting a Fan Clutch

No spin or almost no spin when hot.

Levon Hovagimian
Team Chevelle #279
70 Chevelle SS 454 LS5 4 speed.
Current Engine VortecPro 460 (513 HP) Original is resting
1966 427 Corvette SOLD
1973 Camaro IHRA Hot Rod (LS-6 Auto)11.00 @121 (Chased a 10.99 or better) SOLD

Priddis, Ab. Canada

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