GM alternator pulley: Did I screw up buying this??

[David L.]

Re: GM alternator pulley: Did I screw up buying this??

Dan,

You have a late production 69 Corvette as the production ended in Dec. 1969 which is unusual.

I have a 1969 Corvette Parts Catalog (effective Sept. 1969) but for some reason it does not show the alternator pulleys in Gr. 2.274 which is very unusual. Only the fans and spacer are listed. The 1969 Corvettes w/ 1100796, 1100810, 1100845, 1100847, and 1100849 alternators use fan # 1966990. All other 1969 Corvettes use fan # 3843346. I believe that I have both of these fans in my collection.

If I find some other information about which pulley is correct for you car I will let you know.

Does your car have A.C. or P.S.?

Dave

[Joe L.]

Re: GM alternator pulley: Did I screw up buying this??

David,
The car is an October '69 build L-71 convertible. No power steering. I'm not sure of the 'H.D.' application, L-88?, however based on my knowledge interpreting the listings, I would say the first, 3829387 although it doesn't reference H Perf or SP HPerf. The second listing I think is for a 400HP with air- no P/S. Am I close?

Dan-----


The "HD" does refer to L-88 (or ZL-1). The P&A catalogs are a bit "sketchy" on these pulley applications. However, this is how I think it was (at least, for 1969):

L36/L-68 without N-40 or C-60--------GM #3846180

L-71 (or L-88) without N-40------------GM #3829387

L-36/L68 with N-40, w/ or w/o C-60---GM #3883978

L-71 with N-40--------------------------GM #3829193



GM #3846180 was discontinued in July, 1981 and replaced by GM #3844100. The latter was discontinued several years ago without supercession.

GM #3829193 was discontinued in January, 1973 and replaced by GM #3871242. The latter was discontinued without supercession January, 1988.

GM #3883978 was discontinued without supercession in August, 1999.

GM #3829387 was discontinued several years ago without supercession.

Important configuration details as follows:

GM #3846180---no integral, inside track spacer; 3-3/64" OD; 1/2" groove

GM #3844100----no integral, inside track spacer; 3-7/32" OD; 1/2" groove

GM #3829387---no integral, inside track spacer; 3-5/8" OD; 1/2" groove

GM #3829193----integral, inside track spacer; 3-5/8" OD; 1/2" groove

GM #3871242----integral, inside track spacer; 3-5/8" OD; 1/2" groove

GM #3883978---integral, inside track spacer; 3-3/64" OD; 1/2" groove


I've said many times before that I should stay away from these alternator pulley discussions as I usually get myself in trouble and that was the case here. I was correct in the previous thread post that the GM #3829387 was used for 1969 L-71 without N-40 or C-60 and I was certainly incorrect in this thread when I said that the 3829387 was not used for L-71.

[G A.]

Re: GM alternator pulley: Did I screw up buying this??

Dan,

You have a late production 69 Corvette as the production ended in Dec. 1969 which is unusual.

I have a 1969 Corvette Parts Catalog (effective Sept. 1969) but for some reason it does not show the alternator pulleys in Gr. 2.274 which is very unusual. Only the fans and spacer are listed. The 1969 Corvettes w/ 1100796, 1100810, 1100845, 1100847, and 1100849 alternators use fan # 1966990. All other 1969 Corvettes use fan # 3843346. I believe that I have both of these fans in my collection.

If I find some other information about which pulley is correct for you car I will let you know.

Does your car have A.C. or P.S.?

Dave

No Dave, no A/C or P/S. It is a 3X2 435 horsepower 427. Thanks for the help.

Joe, as difficult as it may be to stay out of the weeds on these things, I really appreciate your time and value your input. Hope you don't think your special, as I too can generate an error from time to time!!

[Mark G.]

Re: GM alternator pulley: Did I screw up buying this??

Guys -

These drawings should help the discussion. The small block crank shaft pulley first belt track is .31" (std) or .37" (shp) from the balancer face. The big blocks drive from the second belt track, 1.14" from the face but P/S changes the offset. Left to right, '387, '180, and '242 alt. pulleys.

[David L.]

Re: GM alternator pulley: Did I screw up buying this??

Marks,

Thanks for the copies of the shop drawings. The 3829387 drawing is also in "The Corvette Restorer" (Winter 2010, page 23).

The dimensions in the 3871242 drawing agree (within reason) with my approximate dimensions as shown in my sketches on my 03/12/2011 post @ 1:23 AM.

My NOS 3844100 pulley measures as follows:
O.D. = 3.20"
I.D. = 1.62"
Hole w/keyway = 0.67"
normal W = 0.83"
Total W = 0.96"

Dave

[Bryan M.]

Re: GM alternator pulley: Did I screw up buying this??

Thanks guys for all your efforts on pulley configurations. By reading all this, I think I finally found out that the pulley that have in my parts stash is a GM #3829193 correct for a L-71 with N-40. It seems to fit all the dimensions in the drawing with the exception radius area around the attachment nut.

[Joe L.]

Re: GM alternator pulley: Did I screw up buying this??

Thanks guys for all your efforts on pulley configurations. By reading all this, I think I finally found out that the pulley that have in my parts stash is a GM #3829193 correct for a L-71 with N-40. It seems to fit all the dimensions in the drawing with the exception radius area around the attachment nut.

Bryan------


If you can, please post a photo of the rear side of the pulley.

[Bryan M.]

Re: GM alternator pulley: Did I screw up buying this??

Bryan------


If you can, please post a photo of the rear side of the pulley.

Here it is.

[G A.]

Re: GM alternator pulley: Did I screw up buying this??

Someone,
Why would the center pulley, in the engineering drawing in post number 34 by Mark Gorney, not show a key way?

[Mark G.]

Re: GM alternator pulley: Did I screw up buying this??

Dan -

The '66 TIM&JG indicates "the base engines use a one piece alternator fan/pulley" and "optional engines use a separate pulley and fan combination." This could be the reason; but I have not had to take one apart.

[David L.]

Re: GM alternator pulley: Did I screw up buying this??

Someone,
Why would the center pulley, in the engineering drawing in post number 34 by Mark Gorney, not show a key way?

Dan,

The pulley keyway was not ever used on any alternators during this era. I believe the keyways were used on generators (1962 & older) but I'm not 100% sure as I have not taken a generator apart in over 40 years.

I have several GM # 1958095 pulleys (including one which is NOS) that were used on 63 Corvette base engines wo/AC that have the keyway. These 1958095 pulleys were also used on 1963-1965 Ser.10-30 Chevrolet trucks w/6 cylinder engines. The 1958095 pulleys that I found on 64-65 Chev. trucks did not have the keyway, otherwise exactly the same.

The 3846180 pulley (the "180" pulley shown in Mark's middle photo) was originally used on the 1964 Chevrolet 409.

Dave

[Joe L.]

Re: GM alternator pulley: Did I screw up buying this??

It's interesting that all or virtually all of the GM drawings for the pullies specify that the part number and broadcast code are to be stamped on the face of the pulley, but very few of the pullies actually have part numbers stamped on them.

[David L.]

Re: GM alternator pulley: Did I screw up buying this??

Joe,

I think that the pulleys sold over the counter did not need part numbers because there was a part number on the box. One less step in the manufacturing process and a cost savings of maybe $0.02/pulley.

Dave

[Joe L.]

Re: GM alternator pulley: Did I screw up buying this??

Joe,

I think that the pulleys sold over the counter did not need part numbers because there was a part number on the box. One less step in the manufacturing process and a cost savings of maybe $0.02/pulley.

Dave

Dave-----


Yes, that's possible. However, unless there was a revision to the specifications and blueprint for the part, the manufacturer should still be making them to the original specifications. Obviously, they are not, though. Also, the drawing for the GM #3871242 shows that the rear of the pulley is supposed to have a "hollowed out" area surrounding the hub (probably designed to reduce the pully's weight). I don't think I've ever seen one of these pullies manufactured with anything but a "flat" rear surface.

In addition, several of the pullies pictured in this thread look to me like they are original pullies and only one of them has a part number stamped (the one that Grant Wong pictured).

[G A.]

Re: GM alternator pulley: Did I screw up buying this??

Dan,

The pulley keyway was not ever used on any alternators during this era. I believe the keyways were used on generators (1962 & older) but I'm not 100% sure as I have not taken a generator apart in over 40 years.

I have several GM # 1958095 pulleys (including one which is NOS) that were used on 63 Corvette base engines wo/AC that have the keyway. These 1958095 pulleys were also used on 1963-1965 Ser.10-30 Chevrolet trucks w/6 cylinder engines. The 1958095 pulleys that I found on 64-65 Chev. trucks did not have the keyway, otherwise exactly the same.

The 3846180 pulley (the "180" pulley shown in Mark's middle photo) was originally used on the 1964 Chevrolet 409.

Dave

Dave -

Ok. By 'not ever used' I think you mean that the keyway was not engaged by the key in the rotor? However, GM by the drawings, continued to require the keyway in 2 of the 3 drawings in Mark's post. Probably means nothing, water under the bridge so to speak, but if GM didn't need the keyway to engage the key why then would they have continued to require it ( the same idea as you proposed on the sometimes missing part number)?
Like you I haven't spilt the case on an alternator or generator in a long time, since 1982, so I don't recall whether or not the pulley keyway engaged the key. If we can get a definitive answer to this question, maybe that would be one more piece of info for ID'ing GM's from the repops????