Jewel or Junk

[Page C.]

Need help to indentify a cast iron crankshaft pulley. It has a casting number 3911549 on it. It is 6 3/4 inches in OD and has 2 groves 1/2 inches wide. It bolts to the crank harmonic balancer. It was on a 1967 small block #657 that was installed in a 1963 Chevy pickup. The group number for this pulleys in 0.659
Thanks,
Page Campbell

[Wayne M.]

Pearl (maybe)

Page -- my July '69 Rev of Chevrolet P & A 30 does not list this # under 0.659. But parts history index shows 3911549 was to be replaced in SERVICE with # 3929697 as of 7-69. This latter # DOES show in my Jan'70 P & A 30B (Corvette only) as being for 1970 Corvette w/H.D. 4-sp., Sp. H/Per.(350). Could be other GM usage.

[Joe L.]

Re: Jewel or Junk

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The GM #3911549 pulley was first used on 1968 Chevrolet medium and heavy duty trucks with small block engine and this use continued into the 1969 model year. It's possible that it was also used for later 1967 MD and HD trucks with small block, but I can't confirm that. As Wayne mentioned, it was discontinued from SERVICE in July, 1969 and replaced by the GM #3929697. This pulley continued to be used in PRODUCTION for L1969 through 1976 Chevrolet medium duty and heavy duty trucks with 350 cid engines.

As far as cars go, the 3911549 was never used in PRODUCTION for any passenger car or Corvette application. Its replacement, the GM #3929697, had only ONE non-truck application. That application was, as Wayne mentioned, 1970-72 Corvette special high performance 350 with HD 4 speed. This translates to 1970-72 Corvettes with ZR-1. However, although GM says that the 3929697 pulley was used for these applications, at least 1 1970 ZR-1 has been reported as not being equipped with this pulley and, instead, being equipped with the GM #3858533. The latter is a near dimensionally identical pulley but it is of stamped steel construction rather than machined cast iron.

So, the GM #3929697 pulley is kind of a "mystery pulley" as far as Corvettes go. It's only theoretically applicable to 56 cars ever built.

I don't know how the 3929697 differs from the 3911549. I have several NOS examples of the 3929697 [none for sale] but none of the 3911549. Since, according to GM, it was a truck-only pulley, I've never added it to the collection.

[Page C.]

Re: Jewel or Junk

Thanks Wayne & Joe for taking the time to research this part. Looks like a recycle to me.
Page Campbell

[Joe L.]

Re: Jewel or Junk

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Just out of curiousity I'd like to compare it to the 3929697. If you could e-mail me some good photos of it that would be nice.