'68-'69 fan clutch

[Everett Ogilvie]

I am familiar with two different length units on midyears; short for big blocks and slightly longer for small blocks. My '68-'69 judging guide does not mention different lengths, so am I to assume there is only one length/style for a '68 or '69, regardless of whether big or small block?

[Joe L.]

Re: '68-'69 fan clutch

Everett----

No, I believe that there were slightly different lengths for big block and small block for 1968-69, too.

Also, most small blocks for 68-70 used a Sweitzer-manufactured fan clutch with a "rectangular, bi-metallic" thermostat. Most, if not all, big blocks used an Eaton-manufactured unit with a "coil spring" type thermostat.

[Everett Ogilvie]

Re: '68-'69 fan clutch

Thanks for the reply Joe. I would like input from others as well, because the judging guide only describes the rectangular bi-metallic style, and makes no comments about 2 lengths. Anyone else? Thanks.

[Dick W.]

Re: '68-'69 fan clutch

Everett, there were also two different diameter clutches, one for AC and one for non AC such as yours. We would normally expect to see the smaller of the two on L/88 cars. We have not done the research to see if both Eaton and Schwitzer manufactured the two styles. Maybe Joe Lucia or Fred Olivia can comment on this.

[Peter L.]

Re: '68-'69 fan clutch

Everett - It is my understanding that from an engineering perspective the fan blade assembly was to be specifically positioned (front to back) in the fan shroud for function and the fan clutch shaft length was designed to to make this positioning "correct," thus the different shaft lengths. The '67 Parts Catalog shows P/N 3814137 (3-7/64" O. L) for the sb engines and P/N 3857530 (2-53/64" O.L.) for the BB engines. The SERVICE P/Ns changed to 3916139 and 3916141 respecively in 01-68. The currently available fan clutch, P/N 3916141, from GM and specified in the '83 Corvette Parts Catalog for both 1960-1970 sb engines and 1965- 1970 BB engines has an overall length close to the original BB fan clutch and therefore it's O.L is shorted than the original one for the sbs. Based on the Parts Catalog information I would expect there were 2 different O.L. fan clutch assemblies for '68 & '69 sbs and BBs. Pete

[Dennis D.]

Re: '68-'69 fan clutch

Joe

Trying to ID these pieces. 022271 sc (Fan clutch)

91 4685 L70 3991427 (fan)

3991424 BY (pulley)

All wrong for my 70 L-46 Found the pulley(3848904) non A/c, PS for me. Need the clutch and fan numbers if you can dig them up. Thanks Dennis

[Jon S.]

Re: '68-'69 fan clutch

Is there any additional data on the use of the Eaton coil-spring type clutch on '69 big blocks? I have been searching for a "correct" Sweitzer clutch for my 69 L88 to replace the Eaton fan clutch I have because the TIM&JG (in fact I just missed one on eBay). I'd love to find out that the one I have is correct after all.

Thanks,
Jon #10673

[Everett Ogilvie]

Re: '68-'69 fan clutch

Thanks Pete. Both the 68 and 69 AIM show 3916139 as the clutch for the small block engines (and two optional parts 3916140 and 5329100). Both AIMs show 3937771 as the clutch for the big block. I suspect the shaft length was one of the differences.

[Jon S.]

Re: '68-'69 fan clutch

Let me try that again. What I meant to say was that I have been looking for a Sweitzer clutch to replace my Eaton clutch because the TIM&JG makes no mention of the Eaton clutch for big blocks. Is there any more info on the application of the Eaton clutch and identification of the correct clutch for my '69 BB?

Thanks,
Jon #10673

[Greg L.]

Re: '68-'69 fan clutch

Everett, My 69 L36 has the "rectangular" style of thermostat as Joe mentioned but I tend to think that it correct, and not the "coil spring" type, for the 427 cars of this period. My car was built Jan 31/69, the engine was built Jan 16/69 and the date stamp on the the clutch flange is 1-21-69. This "rectangular" style is also what is shown on the 435hp engine on page 8 of the 69 sales brochure. Hope this helps.

[Everett Ogilvie]

Re: '68-'69 fan clutch

Thanks for the info - I also think that originals for '68-'69 will have the rectangular bi-metallic strip. Can you check the diameter to see if it is 7.25 please? Thank you.

[Greg L.]

Re: '68-'69 fan clutch

I just measured it and it's 7.25". Let me know if you need any more info.

[Terry F.]

Re: '68-'69 fan clutch

Joe, my 68 390hp has the retangular bimetalic plate type fan clutch on it. It is correctly dated to the car and I strongly believe it to be original. I have owned the car for a long time. Just my input on the subject. I have seen other 68's with bigblocks that had the same. Thanks, Terry

[Terry F.]

Re: '68-'69 fan clutch

I have the same set up on my 68 L-36. Regards, Terry

[Joe L.]

Re: '68-'69 fan clutch

Dennis----

The 3991427 fan was used for 71-73 Corvettes with A/C. The 3991424 pulley was used for 71-74 Corvettes with A/C. I can't identify the fan clutch. However, it's likely a GM #3991426.

None of the above parts will work on a 1970 or older Corvette without significant modifications.