Greg...
 

12 posts in this thread and you accuse me of OCD? You kill me.

YOU know what I am saying is true....
So since they keep saying things directly contradicted by the MB manual... why would you accuse me of OCD.... but not them ?
And I don't care what they choose to do to THEIR cars... my obligation is not to let stand (without a good fight) something which some newbie might believe....

You seem resentful about other's decisions....and compelled to make them 'see the light.'

How does it feel to you when they don't listen?

Dr. Phil time?

I gave up the fight on those marks long ago...other fish to fry, or vibrate as it were. Haw!

I too thought it was settled when Steve Brotherton spoke up about it... but guess it wasn't....

Leathermang,

I've got to stay in Chris's corner and continue to defend my position. I do have the manual in book form and microfiche. In fact I have all the manuals, TDMs, and Electrical trouble shooting manuals from about 1964 to 1992. I used them extensively when I ran my MB repair facility for 20 years after I served my apprenticeship at the dealer. Auto Zentral Ltd. was the name of my company. You need to carefully reread the two sections on surfacing the head and checking timing. Since MB is anal about specs on everything including where the windshield washer squirters spray on the windshield, you know there has to be specs on timing chain stretch. You have to use a little deductive reasoning. The problem I have discovered through the years using these manuals is that someone who knows nothing about cars translates the books because they know two languages. You and I would say " follow these directions carefully". A Mercedes manual will say" work strong to these instructions". The book says use an offset key or replace the chain if it is stetched too far. On the first page it gives specs for the chain. The specs for a used chain is only 2 degrees later than a new chain. That is what you figure MB had in mind. They would never print in the manual to change a chain that is stretched too far, leaving it up to you to decide how much was too far. As to them listing all those keys, MB uses the same pictures, drawings and paragraphs for all models. Ever notice in the picture they show you how to pressure check a cylinder head and you realize the head in the picture isn't even for that engine. Once that list of keys and part #s is typed, it goes into all the books regardless of application. I knew that after I explained it to you, you'd see it my way.:D

Peter

Ok,,, lets take your position on shaving the head and the offset key being used to take up the difference caused by the head being closer to the crank..

1. There are only three relative points on the chain that are important...
2. as long as the chain is tight.... and the total distance between the cam and the crank is adjustable with offset keys...
then the relative position of the IP can be adjusted in the IP....

3. the slack is taken up on the unloaded or backside of this circle... can't you see that the manual internal adjustment provided by the IP.... combined with the offset key capability of setting the cam position realitive to the crank...

that the only problem has to do with the total amount the chain tensioner can take up in backside slack ?

A Double roller chain is an amazingly strong and efficient device... and usually it is a chain rail or slide which gives up due to poor preventative maintenance... rather than the chain that breaks by itself...

If you persist I will have to clog up this thread's downloading ability by posting the pictures of the shop manual.. but hoped to avoid that....

Can you compute the amount of shaving which would have to occur in order to require a different offset key ?

WAY more than any head ever gets shaved...

Boy, you type fast. I'm not disagreeing that these chains aren't strong and that you can't use whatever keys you want and probably be safe. I'm just saying MB cuts you only 2 degrees of slack. A pesimist would say a glass is half empty. An optimist would say the glass is half full. A German engineer would say he designed it that way to be sure that no beer got spilled. About stock removal, remember these keys were not designed just for the diesel engine. The old M130 2.8 liter engines were 85.5 mm thick, and you could machine them down to 84mm. I have used all the keys in the past, and like in says in the book, the keys can be used in either direction. you can also go 18 degrees either way with the cam gear.

"I'm just saying MB cuts you only 2 degrees of slack."

What do you mean by that statement ?

The offsets keys will put the cam into the correct position no matter what the cause of the change.... whether shaving the head, using a thicker head gasket, or chain elongation. ( up to the 10 degrees or so the keys are provided in )...

We are talking about the same thing but you have not figured it out yet...because you don't have a turbo 617 manual to read...
The way in which the chain stretch is measured is by checking the valve position of the number one intake valve when it has moved a specified distance from the head....

The 602/603 FSM procedure requires a dial gauge on the cam follower to measure chain stretch. The difference is that this procedure will ALSO include cam lobe wear! Using the TDC pointer and cam tower marks checks everything else (chain, sprockets, etc) but not the actual camshaft lobe. I did it both ways on my engine, just to compare the results, and I got identical numbers with either method (both performed multiple times, btw.) The 602/603 manual also mentions 2 degrees as acceptable, or "normal", for a used chain (I think 'used' was defined as over 20,000km or something.) Other MB documents show replacement required at 3 or 4 degrees for the 60x engines.

Remember to specify which engine you're referring to, as I think the controversy here is related specifically to the 617. It's still my opinion that you can't really get an accurate measurement of chain stretch with a used chain, since I know of at least two people now who rolled in NEW chains and saw 4-6 degrees "stretch" with a brand-new chain. How the heck do you tell what your "stretch" is, if a new chain doesn't zero things out? Hmmm. Food for thought.


Ya know - what we all need to calm things down is a nice, therapeutic discussion about the benefits of synthetic oils reducing chain and sprocket wear. (struggles to keep straight face)


:p

Chain stretch makes no difference ....
as long as it is not so much that is it not correctable....

That is why they described a " performance objective" ... they wanted the number one valve in a certain position with respect to the crank position...as the way to check stuff out...

Giving the " performance objective " as the means of testing does take into account cam lobe wear also... it is only when this position is not able to be corrected for that one needs to start checking other things in the system...

Yes. With the 61x, the correction is performed with offset keys. With the 60x, the correction is done by chain replacement.


:cool:

Amen ! Thanks.....

Yes, but the offset key correction is only allowed up to 3 degrees.

Gsxr,
Did any of your friends that rolled in a new chain do it to engines that had heads resurfaced? I have replaced many timing chains in MBs in 30 years and never had one come up off the mark unless the head had been surfaced.