1969 L88 camshaft

[Joe L.]

Re: 1969 L88 camshaft

I think the 3879605 was used for 67 and early 68. The 3925535 was then used for the rest of 68 and 69.

Michael----


That's very possible. The 3925535 does look like a 1968-released part number.

[Michael H.]

Re: 1969 L88 camshaft

Michael----


That's very possible. The 3925535 does look like a 1968-released part number.

Joe

Yup, a 3925xxx number would probably be slightly after SOP of the 68.

Somewhere... in all this rubble, I still have (after 40 years) the engine pad date of the change to the new 535 cam.
The text on the document stated that the change was made for reliability and I think it occured very early in the 68 model year.

I think most of the valve train components were changed/upgraded at about the same time, or slightly earlier than the cam??

I remember that there were a lot of issues with the early/67 L88 valve train components.

[Clem Z.]

Re: 1969 L88 camshaft

Duke

I think your right. I think the 3925535 and 3928911 are the same cam. I just dug out more paperwork and the 3925535 is shown as the "service" part number for 3928911. (upper LH corner of sheet) That doesn't necessarily mean it's different than the production cam though, as you mentioned.
There is/was no such thing as a 3928911 in service.

535 cams came in L-88 short blocks from GM and it was stamped on the end of the cam

[Michael H.]

Re: 1969 L88 camshaft

535 cams came in L-88 short blocks from GM and it was stamped on the end of the cam

Yup, I agree Clem. I think the 3928911 number may have been on the drawing but the part number was always 3925535.

[Duke W.]

Re: 1969 L88 camshaft

Duke

I think your right. I think the 3925535 and 3928911 are the same cam. I just dug out more paperwork and the 3925535 is shown as the "service" part number for 3928911. (upper LH corner of sheet) That doesn't necessarily mean it's different than the production cam though, as you mentioned.
There is/was no such thing as a 3928911 in service.

As I said above, one explanation is that the finished camshaft number is ...911, but a finished camshaft without the indexing pin was never available in service. All service camshafts were "assemblies" consisting of the camshaft and pin, and this assembly had a different part number than the finished camshaft.

The finished camshaft number or the last three or four digits are included in the camshaft blank, which was also the "ID number" to identify the blank for proper finish machining. This "ID number" is not the "casting number" as is often stated - a subtle but distinct differentiation.

If you run this this "ID number" through the GM drawing system, and the drawing is still there it will yield a drawing with the detailed lobes finishing dimensions (lift to five decimal places every camshaft degree) and the rough dimensions of the lobes for foundry tooling.

If any one has a known original ...535 assembly, what is the "ID number" on the casting? That is the finished camshaft number without the pin, and I'd bet it is ...8911.

If you run any camshaft "ID number" through the GM engineering drawing system, assuming it is still there, you will get a drawing with all the detailed lobe data.

Duke

[Joe L.]

Re: 1969 L88 camshaft

As I said above, one explanation is that the finished camshaft number is ...911, but a finished camshaft without the indexing pin was never available in service. All service camshafts were "assemblies" consisting of the camshaft and pin, and this assembly had a different part number than the finished camshaft.

The finished camshaft number or the last three or four digits are included in the camshaft blank, which was also the "ID number" to identify the blank for proper finish machining. This "ID number" is not the "casting number" as is often stated - a subtle but distinct differentiation.

If you run this this "ID number" through the GM drawing system, and the drawing is still there it will yield a drawing with the detailed lobes finishing dimensions (lift to five decimal places every camshaft degree) and the rough dimensions of the lobes for foundry tooling.

If any one has a known original ...535 assembly, what is the "ID number" on the casting? That is the finished camshaft number without the pin, and I'd bet it is ...8911.

If you run any camshaft "ID number" through the GM engineering drawing system, assuming it is still there, you will get a drawing with all the detailed lobe data.

Duke

Duke-----


Since they're just about the last cams I'd be interested in using for a street application, I've never looked at one of these L-88 or ZL-1 cams, so I can't speak from any experience with them. However, it would surprise me that there would be any GM casting/ID number embossed on them. These cams were produced in such small numbers it would seem like it would not be cost-efficient for GM to tool up for a specific casting. The purpose of the cam-specific castings was to minimize machining cost. However, with these, it would seem like using a generic core and sustaining the extra machining cost would be more cost efficient.

In fact, in later SERVICE, due to SERVICE-only volume requirements, most GM cams were machined from generic cores. Even though GM already had the casting tooling for the cam-specific cores, apparently it was still not cost-efficient to use cam-specific cores.

In the case of these L-88 and ZL-1 cams, the PRODUCTION requirements were obviously minuscule. More of the cams were probably sold in SERVICE than for PRODUCTION requirements. Even still, the numbers were very small.

Of course, it is possible that specific cores with embossed casting/ID numbers were used. One other thing makes me wonder, too, though. clem mentioned that the a part number derivative was stamped on the end of the cam. With GM cams, usually if a part number derivative is stamped on the end of the cam then there is no casting/ID number embossed on the core.

[Joe R.]

Re: 1969 L88 camshaft

That's the catch! The "complete finished" cam is not what was in any over-the-counter parts source. The only way a camshaft could be purchased was as a camshaft-pin assembly, which was NOT the same number on the casting, which WAS the "complete finished camshaft" (less indexing pin).

If anyone has a ...535 "assembly", what is the "ID number", which is the part number of the camshaft drawing - the complete finished camshaft less the indexing pin.

The above is a subtle point that no one seems to grasp.

Duke

Duke,

Just pulled a 3925535 from it's deep sleep tube and it has 3925535 stamped on the camshaft. Also cast into the camshaft is "23". No four numbers are cast into the camshaft billet as is usual for camshafts.

Also to note it has a groove in the rear bearing surface.

Purchased this camshaft in the 70's. Still new and in it's original tube.

JR

[Clem Z.]

Re: 1969 L88 camshaft

i would not be afraid to bet that these low sales volume cams were made for GM by a outside company

[Michael H.]

Re: 1969 L88 camshaft

Just pulled a 3925535 from it's deep sleep tube and it has 3925535 stamped on the camshaft. Also cast into the camshaft is "23". No four numbers are cast into the camshaft billet as is usual for camshafts.

Also to note it has a groove in the rear bearing surface.

Thought so. Thanks JR. That also answers the question in this thread about the groove in the rear journal. I've had/installed a lot of those 535's years ago but I couldn't remember if there was a groove.

[Art A.]

Re: 1969 L88 camshaft

assembled parts. In other words, if an assembly consisted of cam xxxxxxx and pin yyyyyyy it was issued an ASSEMBLY part number of aaaaaaa. The aaaaaaa assembly part number would only appear on the any paper work associated with that assembly.

[Clem Z.]

Re: 1969 L88 camshaft

Thought so. Thanks JR. That also answers the question in this thread about the groove in the rear journal. I've had/installed a lot of those 535's years ago but I couldn't remember if there was a groove.

all the ones i bought over the counter had the groove because GM did not want anyone putting a non grooved cam in a 65/66 block. even later short blocks and complete L-88 engines had the grooved cam. the 454 460HP crate engines also used a grooved cam. putting a grooved cam in a later block only caused a internal oil leak but putting a non grooved cam in a 65/66 block cause valve train failures.

[Joe L.]

Re: 1969 L88 camshaft

Duke,

Just pulled a 3925535 from it's deep sleep tube and it has 3925535 stamped on the camshaft. Also cast into the camshaft is "23". No four numbers are cast into the camshaft billet as is usual for camshafts.

Also to note it has a groove in the rear bearing surface.

Purchased this camshaft in the 70's. Still new and in it's original tube.

JR

JR-----


That pretty much confirms that it was done just the way I surmised---these camshafts were machined from a "generic" core. In this case, it's probably "generic core #23".

[Richard L.]

Re: 1969 L88 camshaft

For information, I have a late 67 L88 short block, CE over the counter. Block is cast #321. The cam number is 3904367. Cam stamped on the end 4367. Clem verified this unit a while back from his archives.

[Michael H.]

Re: 1969 L88 camshaft

For information, I have a late 67 L88 short block, CE over the counter. Block is cast #321. The cam number is 3904367. Cam stamped on the end 4367. Clem verified this unit a while back from his archives.

The 3904367 is the same number shown for a 67 L88 cam on a GM spec sheet that I have. The part number was 3879605 but the 3904367 appears on some GM documents, and obviously, on the cam, at least for 67.

[Larry S.]

Re: 1969 L88 camshaft

According to my 3-9-72 revision of the Chevrolet Special Equipment manual the L-88 and ZL-1cams in use were 1925535 for L-88 first design chain drive,
3925533 Gear drive for L-88 which should use 3877871 thrust bearing unit and a ball bearing dist. 1111263,
3959180 for ZL-1 chain drive (2nd Design)and.
3994094 chain drive (3rd design). Obviously this is not as early a revision as would answer the question most accurately. Larry