timing the timing chain

[yeager]

I have a 1977 450sl that was in need of a timingchain, upper rails, and tensioner. After reading my manual (vague at best) and nearly every thread posted on this site, I decided to undertake this operation. Everything went smooth up until the point I got help from my wife to feed the new chain over the cam sprocket while I was turning crank with a ratchet. With about half of the new chain in the motor, her hand slipped and the chain came off the cam sprocket. When that happened, both cams rotated due to valve spring pressure. Then a fair amount of cussing took place and my helper was no longer my helper. Since then, I have bought her roses and we are still married. The only way I could figure to get the number one piston to tdc and the cams in the correct position, was to remove the cams so all the valves were closed so I could start over feeding the chain back thru the motor . The passenger side cam came off with no problem but the driver side cam could not be removed because three of the bolts were stripped out. By moving the crank a few degrees then doing the same to the left cam, I got the motor back to tdc and camshaft mark realigned. After reinstalling the right cam, I was able to get the new chain snaked all the way thru the motor and connected to itself with a master link. With this complete, the new rails, tensioner, and chain were installed. I turned the motor over several times with a ratchet and rechecked the timing. When the right cam marks were aligned, the timing indicated 12degrees atdc. I thought maybe the right cam was off one tooth. So I rotated the cam one tooth and it showed 6 degrees btdc. Thinking that the cam sprockets were worn, I replaced both cam sporckets. Doing that had no effect on changing the timing. I then ordered 4 degree offset woodruff keys and installed them. They did little or nothing to change the timing. Next, I used a dial indicator with a probe in the number 1 cylinder to verify that the crank timing marks and the timing pointer were accurate. The dial indicator did show the piston was at tdc with timing mark "O" aligned with the pointer. Forgot to mention, the driver side or left cam marks are aligned perfectly. What do I do next? - sledge hammer, five gallons of gas, matches, case of beer and a big mercedes bond fire. Any help would be greatly appriciated for this frustrated individual.

clik on the DIY link above the procedure is detail there

[ctaylor738]

My experience with my 380 was that the assembly marks will not align until you have tension on the chain, which pulls the chain and the RH cam back a few degrees.

[yeager]

If I did not mention, the new tensioner is installed and I prefilled it with oil while pushing the tensioner piston in and out. Thanks for any help or input you can give me

[Roncallo]

It is very important to only rotate forward when checking timing. If you bring the camshaft marks in line and overshoot the marks do not just go backwards. Go way backward and re approach the marks in the normal direction of rotation.

John Roncallo

[Strife]

Originally Posted by ctaylor738

My experience with my 380 was that the assembly marks will not align until you have tension on the chain, which pulls the chain and the RH cam back a few degrees.

This was true of my 560. I was freaking out until I realized that this would happen.

[ctaylor738]

You need to bring #1 up on TDC and get the pointer alligned with 0 on the balancer. Then be sure the chain is tight and align the left cam on the assembly marks and get the chain on the left sprocket. Then remove the right sprocket, and pull the chain tight and you should be able to slip the sprocket into the chain and put it on the cam with the cam positioned very close to the assembly marks. Then put the tensioner in.

Rotate at least once by hand and verify, then crank it with the starter, which should fill the tensioner and tighten the chain. With a new chain you should have both cams lined up with the timing at 0.

Would not start the engine until you get this sorted out.

[Tomit1]

I had this same struggle a while back with my 450 SEL. I changed the timing chain, tensioner and the upper rails, since there was a considerable slap of the chain at startup.

I think the chain slipped one tooth at the right bank during installation. So I corrected it at the end before joining the chain. It ended being a little late at the timing mark. I then put it one tooth forward then it was a little early. I put it back to the late position, since that was closer to the mark. I drove for a few days, and everything was fine (the motor got a whole lot silent). But there was something wavy on the motor tune, but I am not sure if it was only psychological.

But I figured it was wrong and I opened the cover and put it one tooth forward again at the right bank. (Left bank was always correct and exactly at the timing mark) . And it was a little early relative to the mark. I think now it ran better. As the chain stretches it should get closer to the correct position.

[yeager]

Thanks to everyone that has giving me input on this perplexing situation with engine timing. I have been out of town the last four days so it is time for me to get back to the old Mercedes timing issues.

In responding to the posts, I have only rotated the engine in the normal direction of rotation. If the camshaft marks went past the assembly marks, I would rotate the engine all the way around in the correct direction to realign them.

I have unfortunately tried every thing that ctaylor738 recomended in his post several times and the outcome is always the same. The left assembly marks lign up perfect and the right marks are way off.

Is this just something I need to live with or is there some underlining problem? Could the lower rails, guide wheel sprocket, distributor sprocket, or crank sprocket be worn and throw the timing off to this extent?