#21  
Old 07-14-2020, 10:57 AM
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I've had a water pump let go and dimple the hood, lol.

It also took out the radiator, the fan shroud, the fan, the belt, the clutch on the fan, and the overflow tank for the radiator.

New hood, hood insulation, radiator, clutch and fan, fan shroud, overflow bottle, belt, and $2,000 later, it was back on the road. Would have been more if I had to pay a shop to repaint a new hood.

Luckily this car uses an OEM plastic fan, so instead of going through things or piercing the hood, they tend to just break off.
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  #22  
Old 07-14-2020, 11:23 AM
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Mu buddies 70 flaked the paint off, my 78 the polyurethane stayed on but that big flat surface in black the dimple is obvious-at least to me. Not sure if one of those paintless dent removal things would work on it.

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  #23  
Old 07-14-2020, 05:18 PM
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Old 07-14-2020, 10:17 PM
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There was a thread I was reading advising not to use a clutch but instead a flex fan directly coupled and run it at rpm to improve cooling. Sounds like it could be trouble at a certain rpm

  #25  
Old 07-15-2020, 08:15 AM
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I don't believe there is anything that does a better job of cooling than the factory clutch fan setups Pablo. The added benefit is that they aren't huge HP suckers either.

I have a slew of fans on the wall and on the mezzanine and have tried a lot of stuff over the years. Most recently dual electric fans. I've found out here in the Arizona heat that the factory clutch fan, with a good clutch, and a proper shroud has been the best at cooling hands down, even on big HP large CI engines.

Here's a fan test you might find of interest if guys are worried about HP. I can't think of any other reason someone would switch over to those tiny aluminum flex fans unless they thought they would gain some HP, because they don't really pull much air. As you can see, those little fans don't even add HP. In fact it killed 11 hp over the stock clutch fan.
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  #26  
Old 07-15-2020, 08:54 AM
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Looks like there’s under hood insulation. Slowed it down some.

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  #27  
Old 07-15-2020, 11:00 AM
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The clutch fans have a known RPM limit, about 4800 rpm if I remember right--it's on the Hayden web site if anyone wants to look it up.

Since the water pump is typically spinning faster than the crank...the fan clutch is turning faster than the tach suggests, by whatever the pulley ratio happens to be.

The saving grace here is that the fan clutch is also slipping some, the fan clutch is turning faster than the crank, but the fan isn't due to fan clutch slippage.

Yet another reason to NOT use the "Heavy Duty" or "Severe Duty" fan clutches (that don't slip properly when used with typical automotive fans) in a performance application.

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Old 07-15-2020, 11:15 AM
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I don't know if I buy into all that. These clutch fans are what GM used on nearly all the high performance solid lifter engines and we zing those things up repeatedly. I don't think GM would have engineered them this way if that clutch fan was going to be a problem above 4800 rpm.

My little DZ loves 7,000 rpm. 51 year old stock clutch fan in place, works just fine.

I have the heavy duty unit on my 454 chevelle and can't tell you how many times I've buzzed that thing to 6500 over the last 35 years, lol.

Dad can't stay off the rev limiter set at 6300 in the GTO, with a heavy duty clutch fan on it.

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Old 07-15-2020, 02:05 PM
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From the circle track world...
The crate engine (sealed engine) series all have the same engines so anthing that frees up power or reduces friction/drag is always being sought after.
Those engines max out at 7000 RPM. Anything riveted or "flex" fails in short order.
Fan/pump are usually driven 1:1. Front of cars are completely closed so high draw fan is imperative.

The only two viable choices are;
https://www.race-fan.com/

Crates LAtes and Super Late Models (turning 9000 RPM) usually use this:
https://gorsuchperformancesolutions....ir-6-blade-fan

YFLMV!

On a side note, my factory Ford 428CJ fan/clutch let go on me last summer, ~ @ 6K...it's over driven....
"only" junked a new OEM rad.
Haven't opened the hood since!
(not fixed)


Last edited by STEELCITYFIREBIRD; 07-15-2020 at 02:10 PM.
  #30  
Old 07-15-2020, 02:21 PM
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Quote:
Originally Posted by STEELCITYFIREBIRD View Post
From the circle track world...
The crate engine (sealed engine) series all have the same engines so anthing that frees up power or reduces friction/drag is always being sought after.
Those engines max out at 7000 RPM. Anything riveted or "flex" fails in short order.
Fan/pump are usually driven 1:1. Front of cars are completely closed so high draw fan is imperative.

The only two viable choices are;
https://www.race-fan.com/

Crates LAtes and Super Late Models (turning 9000 RPM) usually use this:
https://gorsuchperformancesolutions....ir-6-blade-fan

YFLMV!

On a side note, my factory Ford 428CJ fan/clutch let go on me last summer, ~ @ 6K...it's over driven....
"only" junked a new OEM rad.
Haven't opened the hood since!
(not fixed)
Those are pretty interesting. The first one is similar in appearance to the OEM plastic fans used today, other than the clutch. I think those plastic blades do have a place.

I tend to believe that's why the carnage wasn't so bad on my sons mustang. Being plastic, it never did puncture the hood. I believe if that was metal it would have certainly went through. When it hit other stuff like the lower radiator hose, the shroud etc...the blades just broke off, didn't even cut through the lower hose. It was the clutch that did most of the damage, mainly to the radiator.

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Old 07-15-2020, 03:16 PM
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I'm guessing very few of these let go at ide but more likely at revs. meaning nothing but bad news..!! Easy sometimes to take for granted the amount of engineering $$ a cars manufacturer puts into its vehicles to insure stuff like this won't happen and make them liable. The lack of this engineering is why some aftermarket parts can be less expensive, sometimes you do get what you paid for....

  #32  
Old 07-15-2020, 04:04 PM
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The Racefan blades are the same material huge semi truck fans are made of. Quite aggressive blade pitch and surface area, VERY light. Heavy fans toss belts. We drive ours with a HTD belt/pulleys ...no slip, ever.
My 68 likely will be getting one in 19".

  #33  
Old 07-15-2020, 05:11 PM
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Quote:
Originally Posted by Schurkey View Post
The clutch fans have a known RPM limit, about 4800 rpm if I remember right--it's on the Hayden web site if anyone wants to look it up.

Since the water pump is typically spinning faster than the crank...the fan clutch is turning faster than the tach suggests, by whatever the pulley ratio happens to be.

The saving grace here is that the fan clutch is also slipping some, the fan clutch is turning faster than the crank, but the fan isn't due to fan clutch slippage.

Yet another reason to NOT use the "Heavy Duty" or "Severe Duty" fan clutches (that don't slip properly when used with typical automotive fans) in a performance application.
Its interesting how the Hayden website says to use both the heavy duty and the severe duty clutch the fans over 2.25" pitch.

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Old 07-15-2020, 07:29 PM
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Quote:
Originally Posted by Formulajones View Post
I don't believe there is anything that does a better job of cooling than the factory clutch fan setups Pablo. The added benefit is that they aren't huge HP suckers either.

I have a slew of fans on the wall and on the mezzanine and have tried a lot of stuff over the years. Most recently dual electric fans. I've found out here in the Arizona heat that the factory clutch fan, with a good clutch, and a proper shroud has been the best at cooling hands down, even on big HP large CI engines.

Here's a fan test you might find of interest if guys are worried about HP. I can't think of any other reason someone would switch over to those tiny aluminum flex fans unless they thought they would gain some HP, because they don't really pull much air. As you can see, those little fans don't even add HP. In fact it killed 11 hp over the stock clutch fan.
Thanks for taking the time to post those attachments Formula. Maybe there will be less unnecessary risk to peoples safety too. I remember seeing a program from the 90's where a guy almost died from a fan coming off and hitting him in the neck. He was luck to have lived.

  #35  
Old 07-15-2020, 10:21 PM
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Quote:
Originally Posted by Formulajones View Post
I don't know if I buy into all that. These clutch fans are what GM used on nearly all the high performance solid lifter engines and we zing those things up repeatedly. I don't think GM would have engineered them this way if that clutch fan was going to be a problem above 4800 rpm.

My little DZ loves 7,000 rpm. 51 year old stock clutch fan in place, works just fine.

I have the heavy duty unit on my 454 chevelle and can't tell you how many times I've buzzed that thing to 6500 over the last 35 years, lol.

Dad can't stay off the rev limiter set at 6300 in the GTO, with a heavy duty clutch fan on it.
The engine is turning 6300, 6500 rpm, but the clutch slips so the fan isn't spinning that fast.

Heavy-duty and Severe-duty clutches slip less, though. (Unless they're used with fans having big pitch/high drag.)


Quote:
Originally Posted by P@blo View Post
Its interesting how the Hayden website says to us"e both the heavy duty and the severe duty clutch the fans over 2.25" pitch.
THIS is what I found on the Hayden web site.
https://www.haydenauto.com/en/techni...q-fan-clutches

Quote:
What is the difference between a standard, heavy and severe duty fan clutch?

Answer: Each fan clutch type is designed to simulate the performance of the original equipment clutch that it replaces. All fan clutches are for specific applications and should be applied only on the vehicle for which they are cataloged. Use of the incorrect fan clutch may result in poor cooling, excessive noise, reduced fuel economy or fan clutch failure.

• Standard Duty Thermal: Turns the fan 50-60% of shaft speed when engaged. Used with fans with lighter pitch (1-1/2" of pitch). Flat plate impeller design with 30 sq. in. of working surface.

• Heavy-Duty Thermal: Turns the fan 80-90% of the shaft speed when engaged for increased cooling. Used with deeper pitch fans (2 1/2" of pitch). Land and groove design with 47 sq. in. of working area allows higher operating RPM's.

• Severe Duty Thermal: Turns the fan 80-90% of the shaft speed when engaged. Used with deeper pitch fans. (2- 1/2" of pitch). Land and groove design with 65 sq. in. of working area. Larger working surface provides cooler running and longer life expectancy.
In other words, don't use the HD--SD clutches with typical automotive fans. The HD--SD clutches will never disengage unless they're driving a high-pitched fan that creates a bunch of drag. Coupled to a fan with less pitch, the fan over-speeds; and it's noisy and wastes power. Maybe even dangerous.

But it will suck a lot of air, so guys use 'em and think they're "great for added cooling". Duh. The thing will never properly disengage. Might as well scrap the clutch and just use a solid spacer if you think you need a "Heavy duty" clutch on a wimpy fan. Don't forget to armor-plate the under side of the hood.

What I did not see was any mention of Hayden selling fans other than electric fans any more. There used to be three part numbers for clutch-style fans, two in the normal direction, and one for reverse rotation. None of the non-electric fans are in the catalog any more.


Last edited by Schurkey; 07-15-2020 at 10:39 PM.
  #36  
Old 07-16-2020, 01:37 AM
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Quote:
Originally Posted by Schurkey View Post
... the water pump is typically spinning faster than the crank...
No. I've NEVER seen a water pump pulley smaller than its crank pulley.

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Old 07-16-2020, 07:26 AM
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Just to add to the confusion Hayden themselves indicated to use the heavy duty clutch for my application.

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Old 07-16-2020, 07:34 AM
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I put a factory judge flex fan on my car with a/c pulleys. At about 3000 rpm`s, I thought the fan might come apart. I got the factory judge pulleys for it. Turn it 5600 to 6000 all the time with no worries. Ya gotta slow those direct drive fans down.

  #39  
Old 07-16-2020, 07:42 AM
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Quote:
Originally Posted by Jack Gifford View Post
No. I've NEVER seen a water pump pulley smaller than its crank pulley.
My new CVF Racing pulleys have the crank pulley much larger. The judge pulleys were a lot closer.

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  #40  
Old 07-16-2020, 07:52 AM
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Quote:
Originally Posted by Jack Gifford View Post
No. I've NEVER seen a water pump pulley smaller than its crank pulley.
IIRC... that is SOP on A/C equipped Pontiac's, over driven water pump....under driven pump on non A/C cars.

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