'63 Fan Clutch

[Irby G.]

Would someone give the part number and an accurate description of the fan clutch for an early '63 (December '62) L76? Nolan's book page 82 states part number 3814560 or 3814137 optional. Is this correct and is it stamped somewhere on the clutch? Any other visual things to look for on a correct clutch?
Aloha and thanks, Irby

[Jack H.]

Re: '63 Fan Clutch

Noland's book is correct. There were two suppliers (primary and optional) for the fan clutch on your car and both PN's are called out in your copy of the AIM (Assembly Instruction Manual). One supplier was Eaton, whose clutch is characterized by a bi-metal actuating coil on the face. The other was Schwitzer, whose clutch uses a flat bi-metal actuating plate. Your copy of the '63-64 Judging Guide should give a description of these parts including specifics about the shaft (length and geometry).

The PN was NOT stamped on the part(s). You have to go by physical appearance being able to distinguish an early production version of the Eaton clutch from later era assemblies which are identical EXCEPT for the shape of the stamped face plate. Some, but not all, clutch assy's were dated via emboss on the side of the mounting flange...

[Irby G.]

Re: '63 Fan Clutch

Thanks Jack.
Going by the judging guide, it appears that I have the original assembly that came with the car. It has the rectangular element on the front along with the stampings "Patented in USA Patented in Canada in 1961 Other Patents Pending" and also the straight fins. The jg states that either of the clutches are acceptable providing the correct shaft length is used but they fail to tell you what that is. Does anyone know the correct length???
Aloha

EDIT... I found the length. At the bottom of the column in the jg it says that the length is 1.8 inches. Time to go take a measurement. Thanks...

[Jean C.]

'63 Fan Clutch bi-metallic strip

Jack, I'm curious about the inner workings of a fluid coupled fan clutch. What is your Fan Clutch 101 take on fan clutches? Am I correct to assume that first the fluid in the clutch is heated by internal slippage, secondly the bi-metallic strip (or coil spring) expands as the result of heat transfer and finally that expansion actuates an internal valve causing the clutch to lock up and thus turn the fan? Specific to the bi-metallic strip clutch, does the strip act on the clutch by flexing the cover to which its ends are attached or by acting on a valve mechanisim that is under the strip and therefore out of sight?
Best regards,
Curious in Spring

[Jack H.]

Re: '63 Fan Clutch bi-metallic strip

There are two places inside the clutch for the fluid (oil) to reside: (1) internal race passage ways (similar to an automatic transmission, and (2) the fluid reserviors (on the Eaton style, coil, clutch these are the 'bulges' in the front face plate on either side of the coil spring. The more fluid in the internal races, the less slip the clutch exhibits.

There are passage ways for fluid to 'leak' from the internal passages back into the reservior(s). As RPM increases, more fluid returns to the reservoirs and the clutch slips more. Also, as ambient temperature increases, the bi-metal expands narrowing the return paths to the reservoirs and slip decreases across the RPM range.

So, the clutch's %-Slip profile changes BOTH as a function of temperature and RPM. The higher the RPM, the more the slip factor is and the higher the ambient temperature the less the slip factor is.

It's actually a pretty simple mechanism that works based on the fluid flow characteristics of the internal oil, how much fluid is contained in the system and the effective diameter of the internal passage to reservoir return path. That's why these clutches tend to become 'loose' as they age, bearing seals wear and they lose internal fluid.

[Jean C.]

Fan Clutch - Thanks Jack *NM*