While working on my Zeniths, I had the valve cover off and noticed the timing chain seems to be stretched. I've replaced many timing belts but the only chained engine I've done was after fatal failure and took much of the guesswork out. I recall hearing somewhere M-B single row chains should be changed to double row chains, is that the case for this engine? If not, is it recommended to replace the timing gears also.?

Next, when replacing, how does one go about physically installing the new chain? I see theres not a typical timing chain cover to remove. I've heard of a trick on older Jags where you link the new chain to the old and turn the old one through until the new one is in. Will this work on my engine? If so, will this work even if I'm changing from single to double row chain?

TIA
Mark

Hey Mark...

Is your timing chain very LOOSE???? My car has sat for a while and my chain is WAY LOOSE. I had my valve cover off and was PLAYING WITH IT. I asked around and figured that my timing chain had jumped a few teeth and thought it needed replaced.....well, what I found out, is that these chains (at least my M114) have a hydraulic tensioner on them. When the engine gets going, it will tighten itself up.

Your chain may be a-ok...

~Christy

I didn't know that but what I saw was lots of slack when you pull the chain that is engaged in the gear. The centre to centre distance of each link grows as the chain ages, ie stretch. When the chain is new you won't be able to pull the links very far out of the teeth of the gear regardless of chain tension.

Well, ok.

All I know is that I can PULL my chain about an inch to the right...and people have said that it's ok to BE LOOSE..

~Christy

The timing chain tensioner screws into the right (Passenger) side of the cyl head. The plunger of the tensioner sits in an oil filled pocket inside the head and, if it's working ok, will keep itself pumped up as the engine runs.
If it hasn't run for awhile, you may have to fill the 'pocket' with oil and bleed (pump up) the tensioner yourself. If you move the tensioner out toward the chain, does it take up the slack?
The single to double row chain conversion is on the 1980-83 3.8 V8 models. (I did one on a 380SL. It took 2 days and required supporting the front of the engine while dropping the front crossmember and oil pan, pulling everything off the front of the engine
includng the timing cover and replacing the chain and every sprocket and chain rail!)

Good Luck,
Mark DiSilvestro

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DrDKW

There is a trick for replacing the chain without dropping the pan, and it involves exactly what you said. You grind a pin out of the existing chain and connect the new one. Being careful to keep tension, you turn the engine until the new chain comes up the other side, the put in the connecting link in.

I read this in an article in The Star on diesels, but I don't see why it wouldn't work on the M130. At least it is worth a try - the only extra effort involved if it doesn't work is the grinding out of the pin.

What are you going to do about the slider rails, though?

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Chuck Taylor
Falls Church VA
'66 200, '66 230SL, '96 SL500. Sold: '81 380SL, '86 300E, '72 250C, '95 C220, 3 '84 280SL's '90 420SEL, '72 280SE, '73 280C, '78 280SE, '70 280SL, '77 450SL, '85 380SL, '87 560SL, '85 380SL, '72 350SL, '96 S500 Coupe

back up a few steps folks.

First off, Christy is right. The chain will appear to be VERY loose if the motor hasn't been run in a while. The tensioner is rather hard oil-filled shock that drops its pressure after sitting a while.

Once the car is running, the idle gear under the cam sprocket will pick up all the slack.

BUT, that has little to do with chain stretch. As the chain ages, the links stretch a little. This alters the timing relationship between the crank, cam and distributor.

By hand cranking the motor to the TDC mark on the crank, you can watch the timing mark on the cam. BOTH should line up when everything is to spec. When the cam is off by a few degrees (like Christy's), you have a stretched chain and that means the valve timing is a bit off.

There are exactly two ways to deal with a stretched chain. One is to replace the chain. There are no shortage of posts in this site's history that describe the procedure. Basically, you grind off a link to open the chain and you feed a new chain in to replace the old. Then you use a master link to seal up the chain. It's not difficult, once you invest in about 200$ worth of tools. The other method is to remove the cam gear and replace the woodruff key that holds it in place. Several offset keys are available for this. However, an old chain will need replacement eventually.

Why? Because chains break. The extreme case is the 380SL that some bean counter specd out with a single row chain. The V8 engines use a very long timing chain, and there are spots where the chain is not supported for several inches of travel. Well, the chain wiggles at 4,000 RPM, so that when it stretches and the chain tensioner does pick up the slack, WHAM, the chain hits something, like a chain rail, and either brakes the rail, or worse brakes the chain.

The single roller v8 chain MUST be converted to a double, otherwise the motor will die some day. The straight 6 chain, being much shorter, and having shorter unsuspended sections will live happily for a long time. And no, there is no double row conversion for it. ALL of benz's straight 6's had single row chains prior to the M130 motor.

-CTH

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http://www.111lakeside.com/