Well today I pulled cam out of my 89 300se and lo and behold the lobes were totally thrashed on #6 and # 5 cyl. wasn't much better along with bad rocker's i only have one question if anyone can help that would be good,before i took apart i wedged a big screw driver down between the chain where they almost come together and you can move the tensioner back very easy so i did so and removed the cam gear easily and left the chain in place while i slid the c-clip towards the top of cam and pulled up and back and it came out very easy,i just don't know if the tensioner should move back that easy ,and with engine running does oil pressure apply to the tensioner to make it go forward,thanks for any help on this.

The tensioner shouldn't move backward, it is a ratcheting mechanism that locks as it "clicks" forward in increments. Sounds like yours is worn out (and may be part of your cam lobe problem?). Though it may have some system of lubrication, it moves forward, as slack allows, by spring pressure only and needs to be reset any time the chain is deliberately slackened (like, by removing the cam gear for example).
To reset it, it must be removed, the pin should be pushed forward through the barrel and placed back in the front again. When you put it back in the car and push the screw cap back in/on, the spring pressure will cause it to seek its own proper adjustment.
When put back in, make sure all the chain slack is on the tensioner side of the cam gear and the other side is somewhat taunt.
Failure to reset it could cause the chain to break in short order.

Also, while you're in there, check the condition of the tensioner rail and chain guides. If the tensioner rail is worn down to metal or moderately scored it should be replaced.

Thanks for the info,i ordered a new tensioner allready but didn't know if i would have to replace or not,now the question is do i have to do any thing to the new tensioner before installing it,thanks much appreciated.

Not really. But take it apart and understand how it works, then it's easy to get it all right. Basically, you install the outer sleeve of the tensioner, then push the piston with the "ratchet" grooves in, and then press the spring in to tighten it up. So, it adjusts automatically when you push the spring down.
By the way, pushing the spring in and starting the threads on the tensioner cap can be fun. You can make a little tool from an old bolt that you can jam in the tensioner cap and wedge against the air pump, to get leverage to hold the spring in place. Grind a couple flats on the bolt so you can turn it with a wrench while it holds the spring/cap in place. You'll see what I mean when you look it over.

DG

are you replacing all the rocker arms and new bolts, also where did you get the cam shaft? Every where I look both parts are big bucks

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I purchased the head from sun valley mercedes dismantler's in los angeles ca. which is only a few hour's from where i live,the head was from a 91 which had the newer style cam and rocker's,i used the cam and the complete rocker tower's with the rocker's on them just put them in the same order they came from the used head,also the tower bolts were threaded all the way up which indicated newer style,it was so easy to do and what a difference the cam and rocker's looked almost like new,the lifter's took a while to pump up because the head was sitting for a while but started right up and quiet as a mouse now,i didn't even pull the tensioner,i just wedged a big screw driver between the chain before i pulled the cam gear and chain off ,of course i put it on tdc first and marked the gear and chain with white out and left the gear on the chain, i rolled the c-clip in front of the cam up to the top and removed it and lifted the cam up and back to pull it through the gear (piece of cake).

Using the rocker towers from another head is a bad idea I think. As far as I know rocker towers are bored and milled on the head so they're pretty much matched with it and won't necessarily match up properly on another head.
Also, holding the chain tensioner's position with a screw driver jammed in it is pretty risky as well. If it slips even a notch tighter the result could easily be a busted chain with lots of damage. It's pretty easy to take out, reset and reinstall. No reason to take such risks.

If it ran for more than a few minutes without breaking, you might have gotten away with it. As far as the swapped towers from another head.... you'll find out if that worked out a little later.

If I'm wrong about that and someone reading knows better, please comment.

The later rockers swap over fine to an early block when used with the matching late cam. I've personally seen it done on 3 early W124 and one 2.6 W201 with no issues. And It's exactly what Mercedes did when they were replacing flat cams under warranty, back in the day. The only difference is the material of the new cam/rockers is hardened properly so you will not eat cam lobes anymore.

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1991 300E - 212K and rising fast...

John - thank you very much for the clarification!
Redrocket - Ya done good!

If I post some advise that I'm not certain of, I always try to make it clear that I may be wrong and solicit other opinions to support or refute it. I'd hate to lead someone wrong on a public forum like this!

Cheers!

Hey --- we all do it. Sometimes I gotta stick my foot in my mouth too. There's some pretty smart people around these forums that aren't hesitant to point things out. Which is good, because most car forums are a minefield of bad advice!

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1991 300E - 212K and rising fast...

I replaced the complete rocker assemblies wiyh the cam,no problems whatsoever,very quiet and runs great,also even though the chain tensioner ratchets it still has about 1/4 inc of play even with spring tension the screw driver will not fall down and only keeps the tensioner in place so that it wont ratchet forward i just pulled back on the tensioner slightly and pulled the cam gear off,i also checked the new tensioner and when you ratchet it forward it stil has about 1/4 inch or more of travel between clicks so easier for me not to have to take the tensioner out,road tested 200 miles man it runs great and this engine is so easy to work on,almost 300,000 miles no leaks and doesnt smoke or use oil it's a great motor.