[BVR421]

"Not only will my SD #922799 (Autozone) clutch engage and disengage at idle speeds, you can actually hear it change speeds while engaged. The car sounds just like it has an electric fan on it...Robert"

thats the way 4 of my cars work. all with factory fans/clutches
1987 F250 SD 460, 1979 Cad Fleetwood 425, 1974 455 GrandVille, 1986 motor home w/460Ford
All sound like a jet engine under the hood when the clutch is engaged.
No clue as to actual temps on those vehicles. The Fords do have temp gauges (C-H), the relative highs and lows seem to run the same summer or winter. The 2 GM cars dont seem to roar as loud as they used to, I think those original clutches are getting worn out. I really like those big clutch fans. Since moving to Tucson I put a piece of tape over any temp gauge with numbers. I dont want to know the actual temp. My heart wont stand it.

[Z Code 400]

BVR421,

Here is something I found interesting about my clutch fan experiment. keep in mind I have a Robertshaw Balanced Sleeve 160° Thermostat.

With 7 Blade Ford Flex Fan 18" Diameter:

Car runs 170°F all the time (above 80°F ambient) and temps will drop to under 170°F when driving past orchards where the water is running or when ambient temps are very low.

The photo attached was taken in December, 2006 and it was around 80°F ambient. This was with the factory Pontiac 5 blade flex fan.

With 7 Blade GM Clutch Fan 18.25" and SD Clutch:

Car runs 180°F to 185°F all the time, regardless of ambient temperatures.

When I first installed the new SD clutch, I let the car idle (98°F outside) and the temp went up to 210°F before the clutch engaged, but it has never done that again. I wonder if it just needed to displace the silicon???...Robert

[Steve C.]

Related, if interested....

See the comments made in Jeff Smith's tech section in the new Sept issue of Car Craft.
It's titled "fan tech". As he comments Jeff has been collecting information on mech and elec fans for years, much has been presented over the years. It includes new testing, this time rear wheel hp on a chassis dyno rather than a engine dyno. Apparantly previous engine dyno testing the bimetric spring on a clutch fan may have been effected by the room temp in the dyno cell. Probably not the same as the hot incoming air temps on the road thru the radiator.

A tid bit....

RWHP with clutch fan at 3600 rpm 211hp, with no fan installed (as with elec fans in place) it was 215hp. At speed with no fan was worth 10 hp.

And yes, they do note there might be a slight decrease in power from the drain from the alternator with elec fans, but it would not have been anywhere near the 10 hp. ( previous testing has shown as low as 1 hp, others vary a bit higher. But it's nothing to lose sleep over, presuming you have a charging system that is capable of delivering 40 to 60 amps output at low speeds according to CC )

Also testing of various flex-a-lite fans.

One example: No fan at 2000 rpm 126 hp, with one "big flex" it was 125 hp.
At speed the same flex fan was down 10 hp

[Z Code 400]

Here are the photos:

Photo #1:

+100°F day 75 mph with 7 blade fan and AC-Delco Severe Duty Clutch

(I also tried a Hayden Severe Duty Fan Clutch and it also kept temps up around 200°F all the time.)

Photo #2:

+100°F day 75 mph with 7 blade Lincoln flex fan

(The car will not ever get any hotter than this, even in traffic, verified by mechanical guage and ray gun.)


Note reduction in oil pressure in photo #2....Robert

[Z Code 400]

Originally Posted by Steve C.

"Also testing of various flex-a-lite fans. One example: No fan at 2000 rpm 126 hp, with one "big flex" it was 125 hp. At speed the same flex fan was down 10 hp..."

That's strange....Robert

[HWYSTR455]

Maybe I'll use one of those ford flex fans on my daughter's cutlass, avoid any 'call-backs' in that area! What's the app and/or part number Robert?


.

[Z Code 400]

This was a NOS unit for a 1968 Lincoln.

[70GS455]

I think the consensus is that the super-duty truck clutches are designed with a higher (like 200 deg) engagement point. I got this from the description of the clutches on the hayden or imperial website. But I was able to lower this point in the unit I have by carefully bending the retaining pin/tang along with the bi-metallic spring itself (in the sharp curve).

[Z Code 400]

Originally Posted by Z Code 400

This was a NOS unit for a 1968 Lincoln.

HWYSTAR,

It's a rather obscure piece. Your friend is correct that all Lincolns were originally equipped with clutch fans during that era. However, there is an explanation. A friend of mine worked for a local Ford dealer for many years. When I was looking for a big 7 blade flex fan, he suggested the one that Ford put on Lincolns.

Apparently, there was a TSB for an overheating condition that provided for a 13 fpi radiator an 7 blade flex fan. The part number, C8SE-8546-B, later crossed to the same 18" fan that was used on the 428 CJ cars, which was available under part number D0TA-C.

Beware of the 19" 7 blade flex fan used on the Boss 429's under part number D0OE-A. That will not fit in the factory fan shroud of a second generation Firebird.

P.S. There is a very common 18" 7 blade flex fan found on mid-1990's Ford Trucks that is constructed to the exact dimensions of the 'Lincoln' fan I mentioned. I have used them on circle track cars season after season, all the way to 8000 without a failure!!!!

Hope this helps...Robert

[Z Code 400]

Originally Posted by 70GS455

I think the consensus is that the super-duty truck clutches are designed with a higher (like 200 deg) engagement point. I got this from the description of the clutches on the hayden or imperial website. But I was able to lower this point in the unit I have by carefully bending the retaining pin/tang along with the bi-metallic spring itself (in the sharp curve).

I think you might be onto something here to be certain. Do you have a drawing indicating what you did????

[70GS455]

Originally Posted by Z Code 400

I think you might be onto something here to be certain. Do you have a drawing indicating what you did????

I duplicated the same procedure I found here:

http://forums.maxperformanceinc.com/...d.php?t=606029

[Z Code 400]

Thanks!

[SD421]

Found this great article which explains why these newer Fan Clutches run hotter and the simple fix....
Basically due to GM reduction the fans are spec'd for 1968 and newer motors where the higher temps are needed for lower emmissions.
This fix now has my GTO getting no hotter than 195 degrees.

http://http://midamericachevelles.co...tch_adjust.pdf

[HWYSTR455]

Link is broke, try this one:

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

That fix was listed here a few years ago, and believe someone actually moved the pin, though can't recall. Some of the tow applications come with the spring already in the second tang/stop, can compare at the parts counter if you have a patient counter person.

.

[Old Blue 66]

Originally Posted by SD421

Found this great article which explains why these newer Fan Clutches run hotter and the simple fix....
Basically due to GM reduction the fans are spec'd for 1968 and newer motors where the higher temps are needed for lower emmissions.
This fix now has my GTO getting no hotter than 195 degrees.

http://http://midamericachevelles.co...tch_adjust.pdf

Which fix did you do? The one with the coil or the one with the plunger design?