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1984 380SL
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The procedure is for cam timing not ignition timing. Rotate the engine by the large bolt in the balancer to exactly 0 degrees (that will put the engine in top dead center of cylinder 1) after the crank is at 0 degrees then check the cam timing marks... both should be at or very near their marks on the cam and cam towers. Sleight variations are not a problem but significant differences are. Post a picture of both cam timing settings when the crank is at TDC and we will be able to determine if corrective action is required. (y)
These pictures show the marks at 2 degrees ATDC as you can see however it's hard to see the exact alignment but i tried to have the camera in the right spot.
 

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These pictures show the marks at 2 degrees ATDC as you can see however it's hard to see the exact alignment but i tried to have the camera in the right spot.
From those pictures your cam timing is nearly perfect. Nothing to be concerned about. (y)
 

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From those pictures your cam timing is nearly perfect. Nothing to be concerned about. (y)
Now I'm really puzzled, I got a new contact in Germany at a guy that has changed about 50 timing chains on these engines and he claims i "must", NOT should, change the timing chain based on the degrees of the lineup given, after i sent him the same pictures he said the same thing as you but mentioned that 8 degrees is quite a lot. I also asked him if it's normal on an engine that only has 80.000 km on it and he just replied, "Normal? the car is over 30 years old". Then he sent me some very unpleasant pictures of the 450SL he's working on at the moment where the valves all where trash where the chain had jumped, claiming he told the guy last year to change the chain but he didn't want to. I would of course prefer not to change the chain yet but I'm at least considering it.

Yesterday i changed the upper plastic sliding-rails on the drivers side and was surprised how easy it was. Well I'll put the distributor back and rotate the engine a couple of times to see how it looks before i decide. I'm gonna order a new chain and tension-er anyway since no matter what i decide I'll have to change it at some point.
 

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My comments were not about the condition of your chain, my comments were on the position of the alignment marks and they look good. Keep in mind, the cam rotates at half the speed of the crank. 10 degrees at the crank is 5 degrees at the cam. In your picture the crank appears to be about 2 1/2 degrees after TDC, which means the cam marks s/b 1 1/4 degrees after dead nuts (about 1 tooth) but they appear to be the proverbial x hair before dead nuts.That would indicate to me that the chain is worn (not stretched) a little but I wouldn't call that bad yet. There are 36 teeth on the cam sprocket, therefore each tooth represents 1 degree of cam rotation. If you had jumped a tooth on either sprocket your cam timing would be off at least a full degree on that sprocket... it's not.. so you didn't jump a tooth.

Having said all that... it's never a bad idea to replace the chain after 80.000 km. On the other hand, chain guides s/b replaced as needed but every 5 to 7 years is a good idea. Time is the enemy of chain guides not miles. It's easy enough to check the guides... they start out life whitish but over time become darker, if you let them go all the way to dark brown your living on borrowed time.

There is little doubt that the chain, guides and oilers are the Achilles heal of this engine. Treat them well and the engine will last many hundreds of thousands of miles... ignore them and the engine will likely end it's life long before it's time.

Replace the chain. Good luck. (y)
 

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36 teeth = 1 degree?

According to shop manual, 1 tooth on cam sprocket = 18deg at crankshaft.

p5 https://www.tonk.ca/r107CD1/Program/Engine/107/M117_45/05-215.pdf
Yes, that's got some of the pieces right... however, the ratio between the crank sprocket teeth to cam sprocket teeth is 2 to 1. Put another way... the teeth are fixed... if the crank sprocket moves by one tooth so too must the cam sprocket move by one tooth, so one complete rotation of the crank sprocket will equal 18 teeth of the cam sprocket rotation... therefor the cam will rotate 180 degrees (there are 36 teeth so each tooth equals 10 degrees) for every complete rotation of the crank sprocket.

I don't believe that's the same as saying 1 tooth on the cam sprocket equals 18 degrees of crank rotation. Perhaps it does and I'm just not seeing it. One tooth on the cam sprocket can only be one tooth on the crank sprocket and because there are 18 teeth on the crank sprocket, each tooth must represent 20 degrees of rotation.

I'm getting a headache. :unsure:

Note: I corrected my finger checks. Apparently simple math and mutliplying buy 10 is beyond my capability. 36 teeth on the cam sprocket = 10 degrees per tooth not 1.
 

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1985 380 SL
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36 teeth = 1 degree?

According to shop manual, 1 tooth on cam sprocket = 18deg at crankshaft.

p5 https://www.tonk.ca/r107CD1/Program/Engine/107/M117_45/05-215.pdf
I am trying to figure out how they came up with 18 degrees. If the cam sprocket has 36 teeth (10 deg./tooth), the crank must have 18 teeth (20 deg/tooth). If the cam moves 1 tooth (10 deg.) the crank must move 20 degrees (1 tooth). For 18 degrees at the crank per tooth there would have to be 20 teeth on the crank and 40 on the cam.
 

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I am trying to figure out how they came up with 18 degrees. If the cam sprocket has 36 teeth (10 deg./tooth), the crank must have 18 teeth (20 deg/tooth). If the cam moves 1 tooth (10 deg.) the crank must move 20 degrees (1 tooth). For 18 degrees at the crank per tooth there would have to be 20 teeth on the crank and 40 on the cam.
I agree, it is almost certainly just a mistake. It would be interesting to read what the German engine manual says - could be something lost in translation. Can't imagine MB engineers making mistakes :)

Jyuma - Your post needs a bit more editing ;) Hope you got over the headache :) This is what it says:
In your picture the crank appears to be about 2 1/2 degrees after TDC, which means the cam marks s/b 1 1/4 degrees after dead nuts (about 1 tooth) but they appear to be the proverbial x hair before dead nuts.That would indicate to me that the chain is worn (not stretched) a little but I wouldn't call that bad yet. There are 36 teeth on the cam sprocket, therefore each tooth represents 1 degree of cam
rotation.

1.25/10= 1/8th of tooth and as established, each tooth represents 10deg of cam rotation.


 

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1983 380 SL
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I agree, it is almost certainly just a mistake. It would be interesting to read what the German engine manual says - could be something lost in translation. Can't imagine MB engineers making mistakes :)

Jyuma - Your post needs a bit more editing ;) Hope you got over the headache :) This is what it says:

1.25/10= 1/8th of tooth and as established, each tooth represents 10deg of cam rotation.
Yup... I know, I was all over 9th grade math and didn't get a single calculation correct. I should turn in my degree. :(
 

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At least we now know how many teeth we have. Good thing at my age.
 

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Wow guys and thanks a lot and great thanks to Jyuma for the detailed explanation!
I got a good laugh and it really made my day!

All parts including the chain have been ordered so work should start next week.
By the way the German guy told me i have to remove all rocker arms on the passenger side so the chain won't jump any teeth on the sprocket when pulling the new chain through. In the manual from Mercedessource it doesn't mention anything about that. Has anybody that changed the chain removed the rockers or not?
 

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My comments were not about the condition of your chain, my comments were on the position of the alignment marks and they look good. Keep in mind, the cam rotates at half the speed of the crank. 10 degrees at the crank is 5 degrees at the cam. In your picture the crank appears to be about 2 1/2 degrees after TDC, which means the cam marks s/b 1 1/4 degrees after dead nuts (about 1 tooth) but they appear to be the proverbial x hair before dead nuts.That would indicate to me that the chain is worn (not stretched) a little but I wouldn't call that bad yet. There are 36 teeth on the cam sprocket, therefore each tooth represents 1 degree of cam rotation. If you had jumped a tooth on either sprocket your cam timing would be off at least a full degree on that sprocket... it's not.. so you didn't jump a tooth.

Having said all that... it's never a bad idea to replace the chain after 80.000 km. On the other hand, chain guides s/b replaced as needed but every 5 to 7 years is a good idea. Time is the enemy of chain guides not miles. It's easy enough to check the guides... they start out life whitish but over time become darker, if you let them go all the way to dark brown your living on borrowed time.

There is little doubt that the chain, guides and oilers are the Achilles heal of this engine. Treat them well and the engine will last many hundreds of thousands of miles... ignore them and the engine will likely end it's life long before it's time.

Replace the chain. Good luck. (y)
Thanks Jyuma, you're absolutely right about the color of the guides. Could you please just explain what you mean by "the proverbial x hair before dead nuts" and how you from this can derive that the chain is worn rather than stretched?
I know that your comments were on the position of the alignment marks and not the condition of the chain. Just as a clarification to the pictures since it's hard to make them look correctly on a photo depending on where the lens of the camera is when the photo was taken.
The drivers side cam lined up perfectly at the 2.5 degrees ATDC on the crank which isn't seen perfectly on the photos. The passenger side cam had the beginning of the groove lined up instead of the bottom of the groove at the 2.5 degrees ATDC. the center of the groove was perfectly lined up at 8 degrees ATDC.
 

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Thanks Jyuma, you're absolutely right about the color of the guides. Could you please just explain what you mean by "the proverbial x hair before dead nuts" and how you from this can derive that the chain is worn rather than stretched?
I know that your comments were on the position of the alignment marks and not the condition of the chain. Just as a clarification to the pictures since it's hard to make them look correctly on a photo depending on where the lens of the camera is when the photo was taken.
The drivers side cam lined up perfectly at the 2.5 degrees ATDC on the crank which isn't seen perfectly on the photos. The passenger side cam had the beginning of the groove lined up instead of the bottom of the groove at the 2.5 degrees ATDC. the center of the groove was perfectly lined up at 8 degrees ATDC.
The chain is made of steel and while it is not impossible to stretch steel using great pressure, stretch is not what accounts for the chain appearing to grow in length... it is the wear of the pivot points of each link. The amount of play between the link and pivot of each link is minor but when you add them all up it can make the chain appear to have stretched. It didn't stretch, it simply wore out and the clearances between each link increased.

In my opinion (I could be wrong) it is far more important to change the chain guides on a regular schedule than it is to replace the chain. When properly serviced (regular oil changes) a chain should last for 100K miles and more, but the guides get brittle with age (not mileage) and are prone to break when a chain grows beyond the ability of the chain tensioner to compensate and the chain slaps into the guides. It is the broken guide that causes the chain to skip resulting in valves hitting pistons. I have never heard of a chain breaking without being caused by a chain guide breaking. I'm not even certain that the chain needs to break for the catastrophic failure to occur. My 380 sucked up valves not once but twice with the second time resulting in a broken piece of chain guide breaking through the top of the drivers side rocker cover.

It is not my intention to suggest that you not change the chain, it's a good preventative maintenance procedure to follow, I only want to stress that chains breaking are not the proximate cause of the catastrophic engine failure scenario.. especially not dual chains... it's more often than not that old brittle guides cause the failure. PanzerPuff posted an excellent video detailing the procedure to follow when changing the chain. There is no need to remove rockers in order to successfully replace the chain.


The proverbial x hair comment is a guttural expression indicative of a very small distance. Notwithstanding the crude way I referenced how close to dead on your cam timing is, it has been my experience that slight variations from perfect with the timing mark alignment is of little concern. They sell offset Woodruff keys for the cam sprockets to makeup for minor misalignment... all but the most anal attentive among us don't bother. Close enough is good enough.

Aside from my inexplicable 9th grade math failure, the fact remains that on a 36 tooth sprocket each tooth represents 10 degrees of rotation and a chain that had skipped a tooth on the cam sprocket would be instantaneously noticeable.

Good luck with your project. (y)
 

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Add worn sprockets to the chain "stretch" equation. Add in a failed tensioner to the catastrophe. I could depress the old tensioner in my '73 with thumb and fingers of one hand.
 

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Tensioner on my car was the biggest problem. It of course keeps chain tight and that compensates for wear. If it is weak, the chain can slop around and as Jyuma said, that is probably the main cause of failures of the plastic guides. I still have the original metal backed guides and they show little wear. I should have changed sprockets, but haven't got around to it. Maybe this summer!
 

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This is really one of the greatest forums, once again thanks for all answers and especially to your very detailed explanation Jyuma, thanks for taking the time.
I've ordered a new chain, chaintensioner and the bent sliding rail for the tensioner, should arrive next week so now i have some time to start tearing down the drivers side.

Does the chain wear in a linear proportion to the cam sprockets? If so would it make sense to change them as well while I'm at it, thinking that the worn sprockets might speed up the wear of the new chain?
I assume there's at least one gear further down along the chain, also there are some plastic sliding rails further down which of course require even more work to get at. Has anybody changed at least the sliding rails and/or the gear down there or are they not so critical?

As a curiosity Jyuma, you write that "My 380 sucked up valves not once but twice with the second time resulting in a broken piece of chain guide breaking through the top of the drivers side rocker cover." How come you let it happen, since you seem to know the reason why or did you just learn this by these mistakes?
 

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1983 380 SL
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This is really one of the greatest forums, once again thanks for all answers and especially to your very detailed explanation Jyuma, thanks for taking the time.
I've ordered a new chain, chaintensioner and the bent sliding rail for the tensioner, should arrive next week so now i have some time to start tearing down the drivers side.

Does the chain wear in a linear proportion to the cam sprockets? If so would it make sense to change them as well while I'm at it, thinking that the worn sprockets might speed up the wear of the new chain?
I assume there's at least one gear further down along the chain, also there are some plastic sliding rails further down which of course require even more work to get at. Has anybody changed at least the sliding rails and/or the gear down there or are they not so critical?

As a curiosity Jyuma, you write that "My 380 sucked up valves not once but twice with the second time resulting in a broken piece of chain guide breaking through the top of the drivers side rocker cover." How come you let it happen, since you seem to know the reason why or did you just learn this by these mistakes?
Good question, and the answer is... I never should have owned a $40,000 dollar car when the average price of a car at the time was under $8,000. I knew nothing and I especially didn't know that Mercedes introduced a car to the US market with serious engineering defects. The first chain went somewhere very close to, but after, the warranty had expired. I thought Mercedes was being generous when they covered the entire cost. Little did I know that they had to do it or face the music about marketing a single row chain version of the 380 but only in the US.

The second time the chain let go was all on my shoulders... I didn't have the money or the understanding of what it took to maintain a Mercedes Roadster of the era so I drove it like it was a Chevy or a Ford... it is neither and I found that out at around 80,000 miles when the chain let go a second time and took a few valves with it and even an injector or two. That's when I had the dual row conversion done on on my own pocket. Ouch!

Shortly after the dual row conversion was done the car developed a serious problem... it wouldn't run above idle.. I still knew nothing about Mercedes so I parked it on the driveway (or was it the backyard?) to wait for me to have the time to fix it... I had other cars I could use. Well, that wait turned into weeks and then months and then into years... it was approximately 20 years, give or take, before I opened the doors again and by that time I had learned that what I didn't know could cost me big time when it came to a 35 year old Mercedes R107 and that's when I found this forum. It's the guys on this forum who are the experts... not me. I don't know anything about an R107 that I didn't learn on this forum, I'm just a little more verbose about it then most. :)

I drove the car all last driving season and even attended the Great Barrington car show in Massachusetts in August but the engine had developed a ticking sound that drove me crazy. I'm currently rebuilding the engine which I'm covering in another thread named "Pull the heads on a 380" or something like that. So once again my 380 is parked but this time with no engine in the engine bay. The engine (well, block) is sitting on an engine stand in my garage and once again the help and guidance of the true experts on this forum is priceless.
 

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1983 380SL, ivory/dk brown, 46k miles, dual roller timing chain. 1986 560SL, red/white, 190K mile.
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Discussion Starter #238
I was like you when I purchased my 1983 380SL brand new.
I had no idea about the timing chain fiasco, but had the perception
that a Mercedes was a finely engineered car.

Still it completely pisses me off when I read that phrase in the Owners Manual:

"You have chosen to drive a MERCEDES-BENZ, a car in whose construction and production we have taken great pains because we believe that quality is not a matter of chance." -- page 3, Owners Manual 380SL
 

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1983 380 SL
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I was like you when I purchased my 1983 380SL brand new.
I had no idea about the timing chain fiasco, but had the perception
that a Mercedes was a finely engineered car.

Still it completely pisses me off when I read that phrase in the Owners Manual:

"You have chosen to drive a MERCEDES-BENZ, a car in whose construction and production we have taken great pains because we believe that quality is not a matter of chance." -- page 3, Owners Manual 380SL
At least you were smart enough to read the owners manual... I didn't even do that. :(
 

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Thanks for your 380SL:s life story Jyuma, very interesting.

With the risk of being thrown out of this wonderful forum by posting the same text twice I'm taking the chance anyway since otherwise the text below could be taken as answered as it drowned in the rest of my text when posted above.

Does the chain wear in a linear proportion to the cam sprockets? If so would it make sense to change them as well while I'm at it, thinking that the worn sprockets might speed up the wear of the new chain?
I assume there's at least one gear further down along the chain, also there are some plastic sliding rails further down which of course require even more work to get at. Has anybody changed at least the sliding rails and/or the gear down there or are they not so critical?
 
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