1968 427 fan clutch

[Mark Stocki]

I'm in search of a fan clutch for my '68 427/400hp. I was told that the clutch is unique to '68/'69 tripowers and the '70 LT1. Would anyone be able to verify (or dispute) what I was told?

Thanks,
Mark

[Joe L.]

Re: 1968 427 fan clutch

Mark-----

It was not unique to the 1968 L-68. The fan clutch was GM #3937771. This is a Sweitzer-manufactured clutch with a "rectangular, bi-metallic plate" type thermostat. It's primary distinguishing feature is a "dish-like" surround of the finned, center section. It was also used for 1968 L-36, and some small blocks with C-60.

A photo of the face of the 3937771 is found below.

[Terry F.]

Re: 1968 427 fan clutch

Hmmm, mine looks different. I think mine is original on my L36, mine also has a date on the bolt flange that matches the car. Believe me, when I purchased the car, nobody had taken the time to find a dated fan clutch. I have also seen others just like mine on other 68's. Am I right to assume that there were two versions used? Two manufactures. I used to be more up to date on fan clutches but it seems to have drifted out of my brain. Mine also has the bi-matallic plate on it as well. I don't recall that appearance of the center section. I believe in 68 there were issues with cooling that were attempted to be resolved with a production change in the 68 fan clutch also. Just a thought to add. Take care, Terry

[Joe L.]

Re: 1968 427 fan clutch

Terry-----

Fan clutches were often an item subject to alternate parts being used on the assembly line. However, the GM #3937771 was the only PRODUCTION fan clutch that I can find ever specified by GM for 1968 Corvette L-36 applications. It's curious, though, because the 3937771 was also used on 1968 L-79 with C-60. Generally, PRODUCTION fan clutches for big block and small block applications of the period had different shaft lengths. I have seen the GM #3937771 fan clutch on 1968 big blocks, though. It's very unlikely that they would have ended up there from SERVICE.

The GM #3916141 was specified as the SERVICE fan clutch for non-C-60 1968 L-36 applications. It's possible that it was also used in PRODUCTION. This is an Eaton clutch with "coil spring" thermostat and no "pie pan" peripheral.

The GM #3857531 was specified as the SERVICE fan clutch for 1968 L-36 applications with C-60. This clutch is similar to the Eaton in general design, but I don't know if it's an Eaton unit (i.e. "coil spring" thermostat) or a Sweitzer ("bi-matllic" plate thermostat).

[Terry F.]

Re: 1968 427 fan clutch

I will have to try and take a picture of mine and send it to you. I remember issures about this a long time ago. I think there were two types of units installed at the factory. Not sure about that though. I have seen several 68's that had low miles and untouched with my fan clutch though. Maybe I am mistaken but I am nearly certain mine doesn't look like the one in the picture you posted. I seem to recall mine is a Sweitzer. I will try to post a picture later. Unfortunately, I will be pushing my photo abilities to the max and I am not sure what I will get since it is installed on the car and the angles are tight. Take care, Terry