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Discussion Starter #1 (Edited)
I replaced my lower crank gear while rebuilding my engine. When I installed the new chain and so on, the timing was <1 degree retarded on the LH side and MAYBE 1 degree retarded on the RH side. This was with used cam gears with 80K miles. I have to believe that a good part of being "off" involves the lower gear. Too bad it's a #$%#% to get at (engine out required). No doubt, this is why Woodruff keys with an offset exist.

A clarification on Woodruff keys; on another thread, it was stated that you needed one offset key on each side. Actually, on the RH side, you need two, and, of course, they MUST be identical (and, of course, in the same direction). The reason for this is obvious when you are installing them (see photo). On the LH side, the "pointer" and the gear are both influenced by the one Woodruff key. On the RH side, there is a spacer between the pointer and the timing gear. So, they should both match, or the pointer will produce incorrect readings. In fact, hey MUST match, because not matching is impossible; the spacer is also keyed, the keyway in it is exactly as wide as the key, and because the spacer is wider than gap between key 1 and 2, the spacer will be impossible to install if they don't match.

I did this, because I was told by an MB authority with >30 years of know-how that advancing the 380's cam three degrees created a noticeable on the butt dyno performance improvement. Because my cams are Euro cams and very different, I was conservative and only advanced timing 2 degrees. This is apparently "legal", because it is mentioned in the MB manual that with new parts or a new engine, this is possible for the first 20K or so.

Supposedly, having the cams not in very, very good sync will prevent the engine from achieving its best performance and the "sync" is rather peaky.
 

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One of the BW Old Guard/R129, W204 Moderator
1997 SL500- 40th Anniversary
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I replaced my lower crank gear while rebuilding my engine. When I installed the new chain and so on, the timing was <1 degree retarded on the LH side and MAYBE 1 degree retarded on the RH side. This was with used cam gears with 80K miles. I have to believe that a good part of being "off" involves the lower gear. Too bad it's a #$%#% to get at (engine out required). No doubt, this is why Woodruff keys with an offset exist.

A clarification on Woodruff keys; on another thread, it was stated that you needed one offset key on each side. Actually, on the RH side, you need two, and, of course, they MUST be identical (and, of course, in the same direction). The reason for this is obvious when you are installing them (see photo). On the LH side, the "pointer" and the gear are both influenced by the one Woodruff key. On the RH side, there is a spacer between the pointer and the timing gear. So, they should both match, or the pointer will produce incorrect readings. In fact, hey MUST match, because not matching is impossible; the spacer is also keyed, the keyway in it is exactly as wide as the key, and because the spacer is wider than gap between key 1 and 2, the spacer will be impossible to install if they don't match.

I did this, because I was told by an MB authority with >30 years of know-how that advancing the 380's cam three degrees created a noticeable on the butt dyno performance improvement. Because my cams are Euro cams and very different, I was conservative and only advanced timing 2 degrees. This is apparently "legal", because it is mentioned in the MB manual that with new parts or a new engine, this is possible for the first 20K or so.

Supposedly, having the cams not in very, very good sync will prevent the engine from achieving its best performance and the "sync" is rather peaky.
Excellent post. Thanks for the info.
One thing needs to be mentioned; the TDC indicator on the crank damper is just for rough approximation of true TDC. While suitable for most work, it should not be relied on for true determination of TDC. Therefore, a degree, or maybe even two, on the cam gears, I think, is acceptable. I would guess the timing between cams should be considered more sacro-sanct.
 

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Discussion Starter #4
What is presently available from MB (and perhaps others) for offset keys is different that that list. The keys are metric, and not unique to MB's or their cams. Also, any "degreeing" of the cams is pointless to that "degree" (so to speak) of accuracy by using the timing marks on the harmonic balancer and the pointer on the water pump. You would have to mount a true degree wheel and find the absolute TDC of #1 (the highest point of travel of the piston) - but this would probably be overkill for anything short of racing.
 

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What I want is to check the chain stretch and synchronize the 2 cams.
Why is that degrees on harmonic balancer is not accurate?
 

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Actually, on the RH side, you need two, and, of course, they MUST be identical (and, of course, in the same direction). The reason for this is obvious when you are installing them (see photo). On the LH side, the "pointer" and the gear are both influenced by the one Woodruff key. On the RH side, there is a spacer between the pointer and the timing gear. So, they should both match, or the pointer will produce incorrect readings.
The most important is understand how the woodruf keys will advance or retard the cam(s) inside the cam sprockets and pointers. I think it is a good idea make a permanent sticker what woodruf keys are installed. I have not made myself this woodruf key sticker yet - every time I read the crank pulley timing marks I can't remember how many woodruf key degrees I have to add/reduce get the real cam(s) timing value.
 

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I would consider 1-4° acceptable late, I would not go advanced.

Unless you are checking cam timing with a degree wheel, finding true TDC
with a positive stop, and measuring piston to valve clearance before & after TDC
at the appropriate specs from an engine builder like Brabus or other Merc tuner.
 

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I would consider 1-4° acceptable late, I would not go advanced.

Unless you are checking cam timing with a degree wheel, finding true TDC
with a positive stop, and measuring piston to valve clearance before & after TDC
at the appropriate specs from an engine builder like Brabus or other Merc tuner.
I'm not trying to do a better setting than the factory one. For my 70/71 cams the attached document says 2mm valve movement at 16° crank angle. I just don't get why the degrees on the balancer is not good enough?
 

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1986 560SL: '84 500SL: '84 280SL 5 speed: other 107s
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I'm not trying to do a better setting than the factory one. For my 70/71 cams the attached document says 2mm valve movement at 16° crank angle. I just don't get why the degrees on the balancer is not good enough?
Degrees on the balancer is "god enough". This discussion just went really technical.
 

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Degrees on the balancer is "god enough". This discussion just went really technical.
I replaced my lower crank gear while rebuilding my engine. When I installed the new chain and so on, the timing was <1 degree retarded on the LH side and MAYBE 1 degree retarded on the RH side.

I did this, because I was told by an MB authority with >30 years of know-how
that advancing the 380's cam three degrees created a noticeable on the butt dyno performance improvement.
It is. But he had perfect timing to begin with at
less then 1 deg on the left and 1 deg on the right retarded

If you want to use non stock came timing the stock
balancer is not 100% accurate.

I have done cam timing on race engines and you would never use the stock balancer.

A real tuner uses a degree wheel with all 360 degrees marked,
 
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