67 Fan Clutch Questions- Help

[Gerard F.]

Got my new 3916141R fan clutch, and have taken my fan assembly off my late (June 30) 67 S/B. Before I disassemble the old clutch from the fan and replace it with the new, I have a couple of questions.

1. Would this be my original fan clutch:



It is an Eaton CJ with what I think is a date code of L12G.
This could have been a replacement in the 1970's as I remember having it in a shop on the cooling system.

Here's the new one from the partsladi:




2. Second question: Is there any special orientation of the fan when attached to fan clutch? On the old one if you look close in the picture, there is a little green paint spot which seems to line up with one of the fan blades. On the new one, there is also some green paint in one location, but on the other side. Thought that maybe the green paint had something to do with the balancing of the fan. Couldn't find anything in the Service Manual on the fan clutch.

3. Finally, I have the 1991 Restorer Article on changing the spring setting to go to the 180d setting. Looks pretty easy to do. Any recommendations on doing this on the new fan clutch? Would hate to put on a new fan clutch and have it run hotter

Thanks, in advance.

[Gene M.]

Re: 67 Fan Clutch Questions- Help

Jerry, I find it interesting the replacement clutch says to store it face down. I was always under the impression correct stowage is same as it would be mounted in the car (standing on end). Learn something new every day.......

[William C.]

Re: 67 Fan Clutch Questions- Help

Based on the configuration of the fins, the fan clutch you took off is an original Corvette item, Can't say as to date.

[Jack H.]

Re: 67 Fan Clutch Questions- Help

(1) Somewhere in the 1971-72 era, the AIM books bear annotations regarding aligning the paint daubs on the clutch to equivalent marks on the water pump hub. Methinks this was a running change 'improvement' to achieve total assembly balance. But, I don't recollect any mention of this orientation process for mid-year cars...

(2) The replacement fan clutch you have is of the later 'improved' Eaton design. See how the fluid reservoirs ('bulges' in the face plate) are roughly trapezoidal in shape vs. the 'square/rectangular' shape of your original? That's the external difference...

(3) There was another thread on 'adjusting' the fan clutch by STRETCHING the bi-metal coil and my advice then (as it is now) is to NOT 'dink' with it. There's a designed in balance between clutch slip and RPM and temperature. When you play with the spring, you're changing the clutch's operating profile and this is a factory fresh unit--leave it as the designer/mfgr intended it to be!

[Wayne M.]

Re: 67 Fan Clutch Questions- Help

I have two CK (BB) Eaton clutch fans, bought mid '80s, early '90s. Both have the green paint sprayed on the fins at one spot on the outer edge of the clutch.

IMO, it's an inspection marking and has nothing to do with alignment to the fan blade assy.

[Larry M.]

Re: 67 Fan Clutch Questions- Help

Gerry:

The L12G date stamp translates to December 12, 1966. Based on the date and the configuration, it appears to be original for a 1967 model car/Corvette.

However, if your car was built in June 1967, there is a significant gap ( 6-1/2 months) between the fan clutch mfg and the car build.

I would have it rebuilt by Fred or Vinny, and keep it as a correct spare. If you want, I am sure you can have them date code it to bring it in a little closer to your cars build date. Something like D12H (April 12, 1967).

Larry

[Mark P.]

Re: 67 Fan Clutch Questions- Help

Gerry - I installed one of these partsladi fan clutches last weekend on my 65 300HP.

I did not adjust it and my car runs at 180 F all the time once warmed up. Just where I want it.

Were you planning to blacken the studs ? I left mine cad but they are supposed to be black phosphate I believe.

Mark

[Rick S.]

Re: 67 Fan Clutch Questions- Help

Jerry,
Werner Meier of Masterworks recommended approx 5 years ago while I was blasting my fan to get it powder-coated as it takes such a beating on a driver. I did and would suggest you consider it as an option while you have it off.
Rick

[Gerard F.]

67 Fan Clutch Questions-Update

Well, I put the new fan clutch on today, unmodified as to the temperature setting as recommended. Figured I'd do a test first, before I changed the setting, which on the bench, is probably a 10 second change. On the car, probably 30 seconds to a minute with eyes on your fingers.

So I did a power run up the hill with the Vintage Air blasting. Used my analog "IR gun" to check the temperature gage:



Actually stole it off my grappa still, and it will probably make its way back, some day.

After the uphill power run, it was only reading 182d. But today was only 85d ambient in the N. CA hills, so not really a test. Need to go through a 100d plus day before I consider a change in the setting.

One thing I found out today, is that the new fan clutch is a little shorter than the original one, enough to effect the length of the bolts which attach the fan clutch to the water pump flange.

When I went to the Vintage Air system, I changed the water pump pulley to this fancy polished cast aluminum pulley. With it came 1.25 " bolts between the fan clutch and the pulley.

With the new fan clutch, the 1.25" length bolts would no way fit into the flange holes, the shortness of the flange shaft would not allow the bolts to go straight into the hole in the shaft, either with the fan on, or off the fan clutch.

So I was about to go to Orchards Supply for some shorter bolts. Then, I thought, what did I do with the original water pump pulley and the bolts that came with it.

Lo and behold, I tore apart the back of the garage, and found this box, appropriately labelled, and inside was my original water pump pulley, and also a zip-lock bag were 4-1" length bolts, white zinc or cad plated with black phosphated lock washers.

Here's a shot of the comparison of the bolts:



For you bolt head fanatics (like me), here is the head of an original 67 fan clutch to water pump bolt:



A S markings with 6 radial lines.

Pardonne the manicure, I'm just having fun.

[Joe R.]

Re: 67 Fan Clutch Questions- Help

Hi Jerry:

Keep in mind that the characteristics of the fan clutch only come into play when the car is not moving or is moving at very low speed. Once the car gets to 30 MPH or more, the air flow through the radiator is dominated by ram air.

So, any differences in the characteristics of your fan clutch will be most apparent at idle, with the A/C on, on a very hot day.

I have read that the original fan clutches were set to achieve minimum slip at temperatures just over 180 degrees, while the 3916141 replacement is set for minimum slip at just over 210 degrees. I have been meaning to ask Fred Oliva whether this is true, and if so, whether an original thermostatic coil could be substituted in the 3916141 fan clutch.

If the alleged difference in the set points is true, I would expect that at idle, you would not get maximum fan cooling until the engine temperature exceeds 210 degrees. Technically this is probably okay, but in terms of your peace of mind in a traffic jam, it might be disconcerting.

[Wayne M.]

Re: 67 Fan Clutch Questions- Help

....I have read that the original fan clutches were set to achieve minimum slip at temperatures just over 180 degrees, while the 3916141 replacement is set for minimum slip at just over 210 degrees. I have been meaning to ask Fred Oliva whether this is true, and if so, whether an original thermostatic coil could be substituted in the 3916141 fan clutch...

Joe -- if you get around to talking with Fred O., could you ask him if he has / uses different calibrations (if applicable) for the specific GM fan clutch numbers discussed in post # 13 of early May thread, link below. These are the variations used in the '65-'70 era.

https://www.forums.ncrs.org/showthread.php?t=60171&highlight=3857530&uid=2206