Ref: 1967 'NOS' L79 Cam GM #3863151

[David K.]

1. Why is this cam stamped #3863151 and not #3863152?
2. Does the minute oxidation on the shiny surfaces render this cam useless? (I can feel it with my finger nail and it does not rub off)

If I had nobody to ask my gut tells me NOT to use this cam for a future rebuild. However many of you guys are far more knowledgeable than me and I welcome your input.

Thank you

Dave Kreps ( 23277)

[Joe L.]

Re: Ref: 1967 'NOS' L79 Cam GM #3863151

1. Why is this cam stamped #3863151 and not #3863152?
2. Does the minute oxidation on the shiny surfaces render this cam useless? (I can feel it with my finger nail and it does not rub off)

If I had nobody to ask my gut tells me NOT to use this cam for a future rebuild. However many of you guys are far more knowledgeable than me and I welcome your input.

Thank you

Dave Kreps ( 23277)

Dave------


This is a legitimate GM cam and it's perfectly fine for use. You should be able to polish off the corrosion on the journals using very fine steel wool and/or crocus cloth. Any discoloration which might remain after removing the corrosion will not be a problem, especially in the continually oiled environment in which the camshaft lives. The corrosion on the end of the camshaft can be removed with a wire wheel.

So, what about the stamped number? Here's the deal: the original camshafts used in PRODUCTION and available in SERVICE during the time the camshafts were being used in PRODUCTION and for sometime thereafter were machined from cores cast in GM foundries. Since all camshafts were being used in fairly large quantity during the period that the camshafts were being used in PRODUCTION, there were specific cores used for each camshaft part number being manufactured. These cores were cast in "near net shape" in order to minimize machining costs. In other words, when the camshafts were being manufactured in large quantity it was more cost effective to cast specific cores for each camshaft profile and, in doing so, minimize machining costs. In the case of this cam the core carried the CASTING number 3863152.

After PRODUCTION use of this and other camshafts ended, the volume requirements for SERVICE-only became so much less. For this the economics of manufacturing became reversed. Now, it was more cost effective to use generic camshaft cores and suffer the cost of additional required machining. At some point, GM ceased producing these camshaft cores in-house and, instead, obtained the cores from CWC, one of the major OEM suppliers of generic camshaft cores. The camshafts were still machined in-house at the Chevrolet Flint engine plant or the GM Bay City engine components plant. At this point, the GM PART NUMBER of the FINISHED camshaft was embossed on the end of the camshafts.

So, this camshaft is absolutely functionally identical to the original camshafts in every meaningful way. If I were going to use a flat tappet camshaft, I would not hesitate to use it. Believe me, no one will ever know that it does not carry the casting number and other casting symbols.

[Duke W.]

Re: Ref: 1967 'NOS' L79 Cam GM #3863151

Dave------


In the case of this cam the core carried the CASTING number 3863152.
.

The ...152 number is the FINISHED CAMSHAFT PART NUMBER, which is the same as the drawing number, which includes the rough dimensions for the core plus all the finished dimensions after machining.

What was sold over the counter - 3863151 is a different number because it is an ASSEMBLY of camshaft and pin. The ...151 drawing is an ASSEMBLY DRAWING - a simple A size drawing that simply shows the front face of the camshaft and the indexing pin.

This applies to all camshafts of the era.

The finished camshaft drawing and the cam-pin assembly drawing may be sequential or close, but could be a couple of hundred apart. It just depended on how the part number requests were cued up in the release system.

The OE (and aftermarket cams like Federal Mogul that are manufactured to the GM prints) are Parkerized that yields a dark mottled gray surface appearance. This process aids break-in because the surface is slightly porous and holds oil, and it wears off after a few hundred miles, which is okay. It was polished off the journals as a final finishing process.

Use a rust remover like navel jelly to remove the actual rust particles from the journals. Then have the journals polished. Small craters from the rust will be left, but should not cause any issues.

Duke

[David K.]

[Michael M.]

Re: Ref: 1967 'NOS' L79 Cam GM #3863151

I have the same camshaft in a GM hard cardboard cylindrical container with sealed metal plugs on each end. Should I remove one sealed end of the container to slide out the camshaft and take a look ?

[David K.]

[Duke W.]

Re: Ref: 1967 'NOS' L79 Cam GM #3863151

The Federal Mogul part number for the L-79 cam is CS-179R, but I don't know if it is still available. Crane also can grind a L-79 cam as they have lobe masters, so they would be my second choice if the F-M part is no longer available.

For current L-79 rebuilds I recommend the L-46/82 cam, which is nearly identical to the L-79 cam but has better lobe dynamics and is indexed four degrees later, IPOML at 114 deg. ATC. Install it with a OE replacement truck roller chain (Made by Cloyes) with the +/- 4 degrees indexing options and install it 4 deg. advance to bring the IPOML back to 110 deg. ATC, same as the L-79 cam. This timing set costs about 25 bucks.

Duke

[Joe L.]

Re: Ref: 1967 'NOS' L79 Cam GM #3863151

The ...152 number is the FINISHED CAMSHAFT PART NUMBER, which is the same as the drawing number, which includes the rough dimensions for the core plus all the finished dimensions after machining.

What was sold over the counter - 3863151 is a different number because it is an ASSEMBLY of camshaft and pin. The ...151 drawing is an ASSEMBLY DRAWING - a simple A size drawing that simply shows the front face of the camshaft and the indexing pin.

This applies to all camshafts of the era.

The finished camshaft drawing and the cam-pin assembly drawing may be sequential or close, but could be a couple of hundred apart. It just depended on how the part number requests were cued up in the release system.

The OE (and aftermarket cams like Federal Mogul that are manufactured to the GM prints) are Parkerized that yields a dark mottled gray surface appearance. This process aids break-in because the surface is slightly porous and holds oil, and it wears off after a few hundred miles, which is okay. It was polished off the journals as a final finishing process.

Use a rust remover like navel jelly to remove the actual rust particles from the journals. Then have the journals polished. Small craters from the rust will be left, but should not cause any issues.

Duke

Duke------


Well, if 3863152 is the finished camshaft part number and 3863151 is the part number for the camshaft + dowel pin assembly, then what was the part number for the raw casting? All GM castings have a part number (which may or may not be seen on the casting). It so happens that in this case the part number for the casting (casting number) is the same as that for the fully machined camshaft. That sometimes happens when a particular casting is used for only one finish machined part. So, one cannot say that the number seen on the casting is only a part number for the casting OR only a part number for the finish-machined part---it's both.

In this case, though, I considered it less confusing to focus on the casting number aspect of the number involved in order to explain why there is a difference between original camshafts and later SERVICE camshafts. Someone might also wonder why if the later SERVICE camshaft had the camshaft ASSEMBLY part number stamped on the end, why didn't PRODUCTION camshafts or older SERVICE camshafts not have the ASSEMBLY part number stamped on the end. The reason, of course, is that they did not need the ASSEMBLY part number stamped on the end because they could be identified by the number cast between the lobes. Later SERVICE camshafts had no such cast-in number since they were ground from generic cores.

Also, personally, I would not use a chemical rust remover to remove the very slight corrosion seen on these journals. I think that polishing with very fine steel wool or crocus cloth is the best way to deal with this. I do agree that any slight pitting or imperfection that might remain will not be a problem.

[Duke W.]

Re: Ref: 1967 'NOS' L79 Cam GM #3863151

All I can say is that I have the ...152 and ...151 drawings, and they are as I stated in my previous post, which I why I keep harping about the subject. I also have finished camshaft drawings and cam/pin assembly drawings for several other vintage cams, and they follow the same pattern.

My description applies to the configuration of camshafts when they were used in production. Later when GM began manufacturing cams from generic cores things changed such as stamping the cam assembly part number at the end of the camshaft, and at some point at least some of the old OE cams like those listed in the GMPP catalogs were manufactured by outside vendors, like Crane.

The core lobe dimension data on the drawing is very cursory. Just a view of the lobe with some specified radii, and I assume that from this summary data the tooling engineers developed the tooling drawings.

The parts catalogs refer to the number cast into the camshaft, like 3152 for the L-79 cam as the "ID number".

If we get chance to get together I'll show you the drawings.

Duke

[Jim S.]

Re: Ref: 1967 'NOS' L79 Cam GM #3863151

Like David , I too have a 151 cam in a GM labeled tube . Don't even remember when I bought it it was that long ago .I decided to take a look at it to see if it was in decent shape and it looks perfect.

However the end numbers stamped into it are 115806 and 240316 with a white dot .

What do I really have ???

[Joe L.]

Re: Ref: 1967 'NOS' L79 Cam GM #3863151

Like David , I too have a 151 cam in a GM labeled tube . Don't even remember when I bought it it was that long ago .I decided to take a look at it to see if it was in decent shape and it looks perfect.

However the end numbers stamped into it are 115806 and 240316 with a white dot .

What do I really have ???

Jim------


The 115806 looks like a Crane part number. So, this may be a GM camshaft manufactured by Crane. At some point, GM probably ceased manufacture of what had become SERVICE-only camshafts and out-sourced them to Crane. Can you post a photo of the label on the tube?

[Jim S.]

Re: Ref: 1967 'NOS' L79 Cam GM #3863151

Hello Joe , Here it is . Either exactly what it says it is or it was replaced/ swapped out and I didnt know any better at the time ? Like I am sooo wise now !.

I looked up that number 115806 on Crane and came up short .

[Joe L.]

Re: Ref: 1967 'NOS' L79 Cam GM #3863151

Hello Joe , Here it is . Either exactly what it says or it was replaced and I didnt know any better at the time ?

Jim-------


Judging by the label, this is a much later SERVICE example of the cam than the one shown in the original post. So, this was almost certainly manufactured after the time that manufacture of the cam was out-sourced to Crane and/or others. This doesn't mean it's bad. I'd say it's the same in every meaningful way as the cams actually manufactured internally by GM.

[Jim S.]

Re: Ref: 1967 'NOS' L79 Cam GM #3863151

Thanks Joe,

I am sure you are correct.

I am sure I picked it up for a good price when I bought it . I guess I will have to live with the fact that I will never realize the hundreds of thousands of dollars I was one day going to get when selling an original , manufactured by GM , 151 cam !

Jim