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Discussion Starter #1 (Edited)
I have a 1972 350SL - Engine #117982-12-002315 a M117.982 engine obviously.

1972SL350 and I opened up the engine to inspect things after my road trip and found a big chip out of one cam lobe and notable wear on a lobe on the other cam. So it is cam replacement or rebuild time.

Bearings and journals generally look almost as new.

My understanding is that this engine is supposed to have camshaft codes 54/55 or 56/57. EPC and MB Classic indicate this engine should have 116 051 52 01 and 116 051 53 01 replacement cams.

The cams we pulled from the engine are codes 52/53, which I understand are supposed to be in M117.984 or M116.991 engines.

The rear cam journals of our code 52/53 cams do not have oil grooves, but our cam bearings for those journals do.

On the other hand, the EPC designated replacement cams mentioned above for the M117.982 engine are the opposite - they have oil grooves, and the associated journals are not supposed to.

Intake and exhaust open and close are different for the 52/53 cams vs. the 56/57 cams.

Questions:

From what I have read, the recommended 116 051 52 01 and 116 051 53 01 replacement cams for the 117.982 engine will not be compatible with the existing bearings for the code 52/53 cams that are in the car. (A 117.984 cam setup).

Is there anything wrong with running a 117.984 cam setup in a 117.982 engine?

What would the effects be?

Does anyone know the original chassis/year/models in which the 117.984 engines were used?
 

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You have an early 117 engine. I get 52 and 53
116 051 53 01 Right
116 051 52 01 Left.

Cam bearings
116 586 04 05 standard
116 586 05 05 require line bore
116 586 06 05 require more line bore.

I will bet they are hotter cams as the later 450's had less and less HP.

Also check you cylinder heads that they haven't been replaced from a later engine.

You should have

117 010 05 20 or 117 010 73 20 for the left
117 010 07 20 or 117 010 75 20 for the right
 

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Discussion Starter #3 (Edited)
Thanks Roncallo,

Heads are still in the engine, so I can't see the part numbers right now. Interestingly, the part numbers for the existing cams are numbered 116 051 46 01 and 116 051 47 01. The codes stamped on the end of the cams are 52 and 53.

Like I said, these appear to be parts for a 117.984 engine. Guess I'll have to get to the head part numbers. Do you know where they are located?

MG
 

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Your cam P/N's are showing up invalid in EPC. This sometimes happens with OEM installed equipment which is never sold as replacement parts or its a sub assembly P/N ie prior to final grind or Heat treat.
 

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Just checked the cams on the '72. 116 051 47 01. The other was hard to read thought it was 48 01 but could have been 46 01. Original 117.982 engine.
 

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Mine are 46/47. Also the rear cam bearings have oil grooves.
Your cams and bearings appear to be the correct ones for the '72 117.982.
 

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I had some cams polished and reground at Delta Cam in Washington. Some people on the W126 forum say "don't regrind/weld an MB cam" but I don't think this is an issue if it's well done. I got them back and they look great and I can't tell where the welding was. They are induction hardened to original hardness and carburized on the surface so they break in OK. I think a lot of people who have problems with regrinds have a problem that caused the cam to wear/chip, and install the repaired cam without really addressing the original problem. Also, on some regrinds, you MAY have to reshim or certainly re-adjust the valves. I would not put a new cam on old cam followers that show any wear. These are expensive new, but I have collected two perfectly good sets for very little money at junkyards.

One thing that you can't really get "fixed" is wear on the cam bearings. They will regrind these to a smaller ID, but then you have to get undersized cam bearings on that side (if MB actually still sells these), and a set (must be replaced as a set) is REALLY expensive. These, too, I've picked up at junkyards.
 
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