Another Fan Clutch Question - 1967

**John D.** · May 1, 2008, 03:49 PM

Re: Another Fan Clutch Question - 1967

Ian,
Yep that's the GM service replacement, I've had one on my car for years. I put the 41 year old original on only for judging. Looks like it's still available from GM with a list price of $243.77 and dealer cost of $144.65 with the price increase on 3/1/08. Hope this helps.

john

**Michael M.** · May 1, 2008, 04:56 PM

Re: Another Fan Clutch Question - 1967

I bought that exact fan clutch from the same ebay vendor. No problems and the part works fine.

**Ian H.** · May 1, 2008, 05:56 PM

Re: Another Fan Clutch Question - 1967

Originally posted by Michael Missailidis (46956)

I bought that exact fan clutch from the same ebay vendor. No problems and the part works fine.

Michael;
Thanks. Are you happy with the appearance (the color of the fins)? They just appear to be too dark in the photo.

**Wayne M.** · May 1, 2008, 06:17 PM

Re: Another Fan Clutch Question - 1967

Originally posted by Ian Hunt (42379)

Michael;
Thanks. Are you happy with the appearance (the color of the fins)? They just appear to be too dark in the photo.

Ian -- IMO, it's just the lighting that makes the back fins seem dark. But if you're worried about that detail, you probably won't like the front configuration at all (see discussion a few days ago -- link follows)

https://www.forums.ncrs.org/showthread.php?t=60072&uid=3205

I'm almost certain that these later production Eaton clutches do not have the square reservoir configuration of the original (optional) factory units of the C2 era.

But as others have said, they work perfectly (I use one as well; GM # 3916141).

But remember these are calibratred for the '68-up engine temperatures of 195 deg F (instead of 180 in earlier years). The maximum slip RPM's are in the 2500 range instead of the 3500 range of the earlier units (with a different part #). This was to reduce noise and HP robbery at higher speed, which happened to be synergistic with the hotter operating temps.

**Michael M.** · May 1, 2008, 06:50 PM

Re: Another Fan Clutch Question - 1967

My '68 is a driver, not a show car. I was looking for functionality. Not sure how dark the metal is on an original fan clutch anyway. Sorry I couldn't help more.

**Mark P.** · April 22, 2009, 10:32 AM

Re: Another Fan Clutch Question - 1967

Does the service replacement have a 5/8 center hole for the water pump shaft or is it 3/4" ?

If it is 3/4" does anyone know if the 5/8 to 3/4 bushing is readily available ?

**Bob R.** · April 22, 2009, 02:46 PM

Re: Another Fan Clutch Question - 1967

I just bought one of these from the parts lady and it has the smaller hole. It fit my 63 perfectly. I had an original fan clutch rebuilt by Fred Oliva a few years ago. This spring I noticed it was leaking so I purchased this unit after getting a recommendation from Joe Lucia. So far it works just fine. From the engine side it would be difficult to tell its not the original but if you look at the front face there are some differences. The size is about exactly the same ass the original.

**Mark P.** · May 7, 2009, 07:16 PM

Re: Another Fan Clutch Question - 1967

I just bought this fan clutch. Should I follow the advice of a 3/25/08 posting on "65 Overheating" and do the following "moving the coil on the fan clutch back a notch changed my temp from 200+ to around 170" ?

**Jack H.** · May 7, 2009, 08:04 PM

Re: Another Fan Clutch Question - 1967

The fan clutch is factory calibrated in three dimensions: ambient temperature, RPM and %-slip to deliver its rated performance profile. When you 'dink' with the spring on a coil clutch, you're changing the 3-D profile of the part...

If the clutch is new, or an original that's been professionally rebuilt, I'd say making 'mods' are ill advised. The 'fix' that's often mentioned for Eaton style (coil) clutches flows from folks with aged cars who are fighting coolant system deterioration as well as fan clutch wear....

**Wayne M.** · May 8, 2009, 08:45 AM

Re: Another Fan Clutch Question - 1967

Originally posted by Jack Humphrey (17100)

....If the clutch is new, or an original that's been professionally rebuilt, I'd say making 'mods' are ill advised. The 'fix' that's often mentioned for Eaton style (coil) clutches flows from folks with aged cars who are fighting coolant system deterioration as well as fan clutch wear....

I suppose, then, the question that could be asked of our "professional rebuilders" is do they recognize and supply the two different temperature calibrations, according to the year of vehicle in wihich the clutch is to be installed.

BTW, there's also a "mod / fix" for the Schweitzer clutches as well. Article appeared in an old issue of RESTORER. Involved sanding a bit of metal off the contact stem of the brass piston, where it contacts the bimetallic strip.

**Jack H.** · May 8, 2009, 02:24 PM

Re: Another Fan Clutch Question - 1967

There weren't two different 'calibrations' for these fan clutches. They were spec'd by GM PN to have a specific temp/RPM profile that that's how they were built. The 'mods' you see published are the result of owners trying to fix cooling system problems resulting from a number of different issues...

**Wayne M.** · May 8, 2009, 05:56 PM

Re: Another Fan Clutch Question - 1967

Originally posted by Jack Humphrey (17100)

There weren't two different 'calibrations' for these fan clutches. They were spec'd by GM PN to have a specific temp/RPM profile that that's how they were built. ..

Calibrations / Specifications --- let me rephrase: as mentioned in my May 1 post of this thread, there were several different "C/S's" over the mid C2 up to 1968 model clutches (#s 3814137, 3814560, 3857530, 3857531, 3916139, 3916141, including short/long shafts) . Do current rebuilders recognize the original "3-dimensional [RPM/engine temp/fan slip]" profile, or is it one size fits all ?

**Jack H.** · May 8, 2009, 07:49 PM

Re: Another Fan Clutch Question - 1967

I can't speak for the other fan clutch rebuilders, but I know Fred Oliva personally. His dad (now deceased) was a CRACK mechanical engineer and gathered the OE spec's with due dilgence for the various PN fan clutches.

In addition to just getting specs, he tooled a test lab (controlled temperature + stroboscope to measure RPM at the clutch drive hub & the attached fan to measure %-Slip) to verify their rebuild process hit the target on the money.

They also hired retired design/sales engineers from Ingersol Rand's Torrington Bearing division who'd worked with both Eaton and Schwitzer to get the formula right for the special bearing and special fan clutch oil that was used to make these puppy dogs work properly.

So, the next time you're shopping a fan clutch rebuilder, ask him for the source spec's he rebuilds to and how he verifies he's using the right parts.

Remember, it's one thing to make a fan clutch look 'pretty' and make it around a 12-mile PV course. But, it's another thing altogether to go take that rebuilt clutch and log +60K miles on 'er including coast-to-coast NCRS National Road tours as I've done...

**Reed B.** · May 13, 2009, 04:06 PM

Re: Another Fan Clutch Question - 1967

Mark Pellowski
To turn the fan on at a lower temperature (using the GM replacement part for a '63), moving the thermostatic coil back is what direction when looking into fan clutch from the radiator?
Thanks,
Reed Brown

Another Fan Clutch Question - 1967

Another Fan Clutch Question - 1967

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