'69 L-36 Fan Clutch ID

[John Blair]

I've searched the NCRS site archives and haven't come up with much on 1969 L-36 fan clutches. I'm trying to find a correct fan and clutch for my car, but I'm not real clear on what correct is for a '69 L-36 with air. Bizzoco's 1969 Stingray Guidebook seems to suggest that this car had a clutch with a bi-metallic strip and a "starburst" sort of stampting on the face (he has a picture, but the caption says that the clutch pictured is "similar to the 1969 big block OE fan clutch"). But he also says "CK is the code listed in the parts manual for the high performance 350, 427 thermostatic coil fan clutch," which seems to suggest the 427 had a coil rather than a strip.

Can someone tell me what I should be looking for, what it should look like, codes, etc?

Thanks!

[Joe L.]

Re: '69 L-36 Fan Clutch ID

John-----

The original L-36 fan clutch was a GM #3937771. This was a Sweitzer-manufactured fan clutch which used the retangular, "bi-metallic" plate on the front and the "starburst" pattern. I don't know what the broadcast code was for this unit.

[Jack H.]

Re: '69 L-36 Fan Clutch ID

Check your copy of the '69 Assembly Instruction Manual (AIM). You'll find the base engine fan clutch called out in Section 6. If the fan clutch changed due to configuration (BB engine or A/C), then you should find correcting call outs for the clutch in those option sections of the AIM.

Typically, there were 2-3 qualified suppliers of a given fan clutch. On the AIM page where the fan clutch is, you'll find an item number that refers to the parts list on that drawing. When multiple suppliers were recognized for fan clutches, the first is identified by a PN next to the part item number. Second and third alternate sources are listed below with an [OPT] designation followed by the applicable PN.

Eaton was one supplier and their clutch was actuated with a bi-metal coil. Schwitzer was another common supplier with their clutches actuated by a bi-metal bar. Delco Remy actually got into the fan clutch business ('clone' of the Eaton coil clutch) and you'll occassionally find [OPT] designations in Corvette AIM books for a third fan clutch with a radically different PN sequence from the other two--this is the Delco unit.

The above is why there's controversy on what's 'correct' (coil or bar) in terms of fan clutches. The truth is, in any given year any of the three mfgr sourced clutches could have shipped from the factory on a Corvette and all should be treated as 'correct' based on AIM data.

[Craig S.]

Re: '69 L-36 Fan Clutch ID

John - make sure you don't confuse the Ford radial finned front Schweitzer clutches with Bimetallic strip for the starburst Chevy version. I have a correct 66 big block Schweiter clutch and could take a picture of the front for reference if you wish...Craig

[John Blair]

Re: '69 L-36 Fan Clutch ID

Thanks Joe & Jack. I did check the AIM, but it doesn't seem to make a clear distinction about big block vs. small block clutches. On page J208 in Section 6, it lists 3916139 as the clutch assembly, with two "OPT" PNs--none of them, strangely enough, is the 3937771 number that you gave me, Joe, which makes me think that they're all small block numbers. This is the only page in my AIM with fan clutch PNs.

On a related topic, Bizzoco shows the small block clutch as having a date code on the mounting flange. Is the date code location on the BB clutch as well, and is it a Julian date code?

Thanks again, guys.

[Joe L.]

Re: '69 L-36 Fan Clutch ID

John-----

If you check out page J371 (UPC L-36, sheet A7) of the 1969 AIM you'll see reference to the GM #3937771. That's not where I got the information which I provided in my previous post, but it does confirm it. No optional units are specified.

The GM #3937771 fan clutch was a Sweitzer-manufactured unit. This fan clutch was also used on other applications, including 1969 with L-46.

Usually, Sweitzer clutches have a date code on the edge of the mounting hub. I've forgotten the format, but I don't recall it as being a julian type format.

[John Blair]

Re: '69 L-36 Fan Clutch ID

Ah, I see. Thanks, Joe. It never occured to me to look for the big block specs under "optional equipment" in the AIM, though it certainly should have since it was an optional engine.