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

[Old Goat 67]

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

[mgarblik]

Excellent information, thank you.

[Tim Corcoran]

Nice article thanks for sharing. I have had this problem in the past and returned the clutch and exchanged it for the HD unit and it solved the problem and cuts in at the proper point for 180 operation.

[SD421]

Thanks Old Goat 67 for fixing the link

[STEELCITYFIREBIRD]

Good stuff,thanks!

[rohrt]

That is best tip I have seen in a while.

Just added to my notes.

[torqjunki]

Nice....gonna go out and look at my clutch now. Would be great if it works for me. Thanks

[torqjunki]

Not clear on what direction to spin the coil. THe center pin will rotate either direction when I spin the coil. Should it be clockwise or counter clockwise?? My clutch may just be faulty although it is very new.

[SD421]

Originally Posted by torqjunki

Not clear on what direction to spin the coil. THe center pin will rotate either direction when I spin the coil. Should it be clockwise or counter clockwise?? My clutch may just be faulty although it is very new.

You want to make the coil tighter so it reacts faster . Mine is clockwise
See pic

[b-man]

Now we need somebody to do this mod (and only this mod) and report back how much it actually reduced your normal operating temps, if at all.

[SD421]

Originally Posted by b-man

Now we need somebody to do this mod (and only this mod) and report back how much it actually reduced your normal operating temps, if at all.

Bart, I did the mod Sunday night and yesterday drove the car around for over an hour and usually it can get up to 210 degrees but it wouldnt go over 195 ish

[b-man]

Originally Posted by SD421

Bart, I did the mod Sunday night and yesterday drove the car around for over an hour and usually it can get up to 210 degrees but it wouldnt go over 195 ish

Excellent, nice measurable improvement.

Be sure to let us know if you see that same 15 degree difference continue over time.

Hopefully others here will report back with similar results.

[Gary H]

I read the article and I'm a little confused. It says in the top left picture of page 63 in the article that the valve in the center will rotate when you turn the spring to a different slot. But it says at the bottom of that same picture text that the center valve won't rotate. On my severe duty Murray fan clutch I can easily turn the spring and center in either direction, no tention. Not sure it's really doing anything. Oh, the fan clutch only has about 30 miles on it, it's new.

Can someone explain to me how to perform this procedure?

[68 Firebird]

i heated the coil to view direction the spring would rotate center pin.
then moved outer spring to get center pin rotated abit to then activate sooner.

[crm318]

Same here. I unhooked the coil and as I turned it and it turns shaft in the center. It pops as I turn it, but no real resistance.

[Gary H]

OK, I took my brand new Murray clutch fan back off the car and did this modification. I took a hair drier and heated the coil to see which direction it would rotate the center pin when heated. In my case it was counter clockwise. I took the coil loose from the outside slot it was in from the factory and rotated it CCW just to the left of the casting which the outside coil was located in (total distance moved was only about 3/8"). I then placed some JB weld on it to hold it in place at the new location. The result was that the clutch engages now much earlier and keeps the car at around 180 versus the previous 195. In addition, I called Murray and spoke with their tech department to ask them about this modification prior to doing it. In a nut shell,the tech said that it would work but discouraged me from doing it since"they spend thousands of dollars on research to get this things right"

The only negative so far is that the fan clutch stays on more than normal, is a little noisey, and may rob a little HP. Definately cooler though.

[torqjunki]

Thanks for the update. I purchased a new Murray clutch and installed it. It appears that Hayden is now Murray. I installed it without any mod. I have not been able to drive the car much due to some other issues, but I see some improvement already. No more belt sqeek!

[pfilean]

My fan clutch is a Hayden 2747 which is supposed to be a heavy duty unit. But the coiled spring outer coil has only one slot to put the bent coil end into. I can move it clockwise (looking from the front of the engine) and get a kind of funky grip around the mounting tab. Or I can move it counter clockwise and have it just rest against the mounting tab. The coiled spring will get longer when heated and so the clockwise change would not transfer any movement to the valve at the center. And a change counter clockwise might cause a change in the operation of the valve but the spring would not rotate the valve back to original position when cooled.

So which way is the movement supposed to be? Clockwise or counter clockwise? The article says move to the other slot position and I suppose if you had two possible slots (the pictures show Eaton) it would be obvious. Anybody done this yet on a Hayden?

[Blued and Painted]

If you restrict bi-pass coolant flow at heater core and intake to timing cover, forcing more coolant through the radiator. then clearance the divider plate to water pump, you wont need a fan except for stop and go. IMO.