Fan Clutch 1968 - 1969

[Mark F.]

I have two fan clutches. One dated 4-8-68 SC that has a 7 1/4 inch diameter and one dated 8-19-69 SC with a diameter of 6 inches. The judging manual is silent on the size of the fan clutch. Was there a change between the 68 and 69 fan clutches? Are these correct sized clutches for the 68 and 69 model years? Both have the straight fins. I don't know if it makes a difference but the 68 clutch has a 2 1/4 inch mounting flange with holes (not slots) and it currently has a five blade fan attached. The 69 clutch has a 2 1/2 inch mounting flange with holes.

Thanks

Mark Franken

[Joe L.]

Re: Fan Clutch 1968 - 1969

I have two fan clutches. One dated 4-8-68 SC that has a 7 1/4 inch diameter and one dated 8-19-69 SC with a diameter of 6 inches. The judging manual is silent on the size of the fan clutch. Was there a change between the 68 and 69 fan clutches? Are these correct sized clutches for the 68 and 69 model years? Both have the straight fins. I don't know if it makes a difference but the 68 clutch has a 2 1/4 inch mounting flange with holes (not slots) and it currently has a five blade fan attached. The 69 clutch has a 2 1/2 inch mounting flange with holes.

Thanks

Mark Franken

Mark-----


There were several different fan clutches used on Corvettes over the 68-69 period. Some of these were Eaton-manufactured pieces with "coil spring" thermostats and "curved" fins and others were Sweitzer-manufactured pieces with "bar-type" thermostats and "straight" fins. Yours are obviously the Sweizter style but there were also several different Sweitzer style clutches used.

However, ALL 1960-70 Corvette fan clutches use a clutch hub-to-waterpump hub bolt pattern with a 1-3/4" bolt circle whereas all 71-82 use a 2-1/8" bolt circle. I'm not sure what the measurements that you've provided represent but I suspect they represent the difference between these 2 bolt patterns, since these were the only 2 SAE size patterns ever used for any Chevrolet application that I'm aware of.

While there were no 1968-69 Corvette applications that used the larger bolt pattern, there were some other GM applications of that period that did. So, I expect the 69 dated piece you have was not originally installed on any Corvette. Whether the 68 piece you have is correct for a Corvette, I do not know, but it's possible it is.

[Mark F.]

Re: Fan Clutch 1968 - 1969

The 68 piece does have the 1 3/4 inch bolt pattern. I'm still a little confused as to why the diameter of the finned areas (7 1/4 inch vs. 6 inch) are so different on the two years.

Thanks Joe

Mark

[Joe L.]

Re: Fan Clutch 1968 - 1969

The 68 piece does have the 1 3/4 inch bolt pattern. I'm still a little confused as to why the diameter of the finned areas (7 1/4 inch vs. 6 inch) are so different on the two years.

Thanks Joe

Mark

Mark-----


As I mentioned, there were several different configurations of clutches used for Corvettes during the 1968 and 1969 period. Plus, the one you have dated 1969 is likely not even a Corvette fan clutch which opens up the "universe of possibilities" to an even greater degree.

The Sweitzer clutch used for many L1968 and 1969 big blocks had a "pie pan" configuration on the face and was, thus, of larger OD than the Sweitzer clutches used for most small blocks and some big blocks.

Pictures of the clutches you have might help us provide further information.