C2 / early C3 Fan Clutch identification

[Wayne M.]

Here's what I believe is a small block '69 clutch, of the Schweitzer(sp ?) design [bimetallic strip] dated 10.6.68_SC (Oct 6th 1968) on the flange edge (see link below). When I cleaned off the grime, the letters "CJ" appeared (see top of autoload pic). I understand from the '65 TIM&JG that flange dating started around mid (calendar ?) 1965.

I understand that "CK" indicates big block usage, and I have a few of the bimetallic coil design (Eaton) with this coding (but Eatons have no flange edge date coding).

On the one shown below and in the link, shaft and fan mating flange dimension to W.Pump pulley is 1.75", which I guess confirms the small block application.


There was another on eBay recently with a dating of 7.27.68_SD, also claimed small block application.

My question is what is the correlation between SC, SD and CJ, CK ?

[Joe L.]

Re: C2 / early C3 Fan Clutch identification

Wayne-----

Broadcast coding on these fan clutches was generally related to application and not to a specific part number. So, for any given broadcast code, there might be several clutch part numbers and configurations. In any event, the "CJ" broadcast code was applicable to 63-70 Corvette small block applications as well as other Chevrolet applications. However, I don't think that the broadcast coding began as early as 1963. I think that coding began for the 1967 model year, but it may appear on some earlier clutches.I suppose at that time there were so few different fan clutches during 63-65 they didn't need broadcast coding to ID them for the line. The "CJ" clutches have the "long" shaft, about 1.8" in length. "CJ" clutches were mostly Sweitzer bar-type, but some may be Eaton coil.

The "CK" clutches were the used for 1966-70 big blocks (for 1965, I think that the clutches were the same for big block and small block; I don't think that they'd "figured out" the "need" for a shorter shaft length yet). As with "CJ" type, they could be either bar or coil thermostat, but I think that most "CK" were coil type. Shaft length was about 1.4".

A few more:

"CT"= 66-68 big block, usually with C-60; Eaton or Sweitzer

"CH"= 1971-only fan clutch; most, if not all, Sweitzer

"CA"= 1972+ without HD cooling; Eaton

"AX"= 1974+ with HD cooling; Eaton

"AZ"= 1976-81 without HD cooling; Eaton

"AA"= 1979-81 without HD cooling; Eaton

I've never heard of an "SC" or "SD" broadcast code, but that does not mean it didn't exist. In the context you describe with the date code, the "SC" usually refers to Sweitzer Clutch. I suspect that "SD" is someone reading this incorrectly or an incorrectly stamped code.