When is the right time to install a new timing chain? - PeachParts Mercedes-Benz Forum

Tanksowner · #1 01-12-2011, 06:48 AM

I've been thinking about this a lot lately. I've seen pictures of engines after the chain snapped, and really caused some damage. If I'm at 167K now, about how long should I wait to do the timing chain?

ForcedInduction · #2 01-12-2011, 06:49 AM

There is no time. When the chain passes 8 degrees elongation its time to consider it. Keys are available to correct up to 10 degrees.

Use synthetic oil and you may never need to change it.

Stretch · #3 01-12-2011, 07:21 AM

Quote:

Originally Posted by ForcedInduction

There is no time. When the chain passes 8 degrees elongation its time to consider it. Keys are available to correct up to 10 degrees.

Use synthetic oil and you may never need to change it.

Meaning your engine will be so well lubricated the chain will hardly stretch?

ForcedInduction · #4 01-12-2011, 07:32 AM

Yes. Synthetics are light-years ahead of dino oils.

MTUpower · #5 01-12-2011, 07:54 AM

Quote:

Originally Posted by Tanksowner

I've been thinking about this a lot lately. I've seen pictures of engines after the chain snapped, and really caused some damage. If I'm at 167K now, about how long should I wait to do the timing chain?

I just did mine with the same mileage, plus the banana rail.

vstech · #6 01-12-2011, 08:56 AM

Quote:

Originally Posted by Army

Meaning your engine will be so well lubricated the chain will hardly stretch?

keep this in mind when trying to understand this effect.
the chain does not stretch.
the gears and links wear. quality oil and proper filtration/changes prevent wear.

Stretch · #7 01-12-2011, 09:27 AM

Quote:

Originally Posted by vstech

keep this in mind when trying to understand this effect.
the chain does not stretch.
the gears and links wear. quality oil and proper filtration/changes prevent wear.

I don't want to appear to be too stubborn - but - my experience with bicycle chains is that they do stretch as well as wear into the sprockets. Most of the time I see that the chain links are more worn than the surface of the sprockets but I think the death of a bicycle chain (at least) is that the links get bent / stretched out of shape. I'm just transferring my bicycle experience to an OM617! (Heaven help us)

vstech · #8 01-12-2011, 09:31 AM

ha! yeah, I'm sure it is the case with bike chains. but the MB chain literature I've read states plainly that "stretch" is a misnomer. the length of the chain is unchainged...(sorry for the pun) it's all in the wear of the contact parts.

actually, now that I think on it... I'll bet the bike chains remain the same length also... the outer links would have to actually stretch to increase the length of the chain. what's gotta be happening is the rollers ride on the pins, and the wear on the inside of the rollers, and the pins, and the teeth of the gears all wear. the overall length of the chain itself remains unchanged.

no?

ForcedInduction · #9 01-12-2011, 09:35 AM

Bicycle chains are not quite like timing chains. A bike chain has to have some side play for it to change sprockets and move with that nonlinear working line.

Quote:

the length of the chain is unchainged

Not quite... the number of teeth (drive ratio) doesn't change but the total length does.

babymog · #10 01-12-2011, 09:42 AM

The chain does not stretch (bicycle or timing), but it does change length. As the pins and holes wear, there is more clearance and thus the chain becomes longer.

On a bicycle, like a timing chain, when you can lift the chain in the middle of the sprocket/gear with it being tight on both ends, the chain is "stretched" and should be replaced. When the chain becomes longer or "stretched" if you prefer, you have two problems: One is the timing change (retarded valve and injection timing), the other is that the chain now pulls on only the last tooth of the sprocket/gear, causing more stress & wear to the teeth. A proper chain will distribute the wear better and the gears last longer.

Stretch · #11 01-12-2011, 09:52 AM

Whilst you were writing your responses (thanks - a lot clearer now) I found this (which may be of interest):-

http://chain-guide.com/

ForcedInduction · #12 01-12-2011, 09:59 AM

MB only says "excessively elongated", but I have never seen an official description as to what "excessive" actually is.

They provide keys up to 10*, but I'd be hesitant to use something that large. I've only used the 4* keys in both my cars.

vstech · #13 01-12-2011, 10:05 AM

yeesh! 10° would be a really late timed injector...

winmutt · #14 01-12-2011, 11:36 AM

Any chain will stretch with enough force placed on it, hence motorcycle chains. Usually wear is based on contact surfaces as stated above. I am pretty sure that its a combination of both as a 10* offset would be something like a centimeter of elongation measured between the cam and crank. I find it very hard to believe that they dont stretch period.

whunter · #15 01-12-2011, 01:38 PM

Quote:

Originally Posted by babymog

The chain does not stretch (bicycle or timing), but it does change length. As the pins and holes wear, there is more clearance and thus the chain becomes longer.

On a bicycle, like a timing chain, when you can lift the chain in the middle of the sprocket/gear with it being tight on both ends, the chain is "stretched" and should be replaced. When the chain becomes longer or "stretched" if you prefer, you have two problems: One is the timing change (retarded valve and injection timing), the other is that the chain now pulls on only the last tooth of the sprocket/gear, causing more stress & wear to the teeth. A proper chain will distribute the wear better and the gears last longer.

More data on this topic..

Timing chain stretch does not exist
http://www.peachparts.com/shopforum/showthread.php?t=163604

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