OK, my car has 149K and I'm scared of a Total Engine Wreck, so I onened it up. The timing chain looks tight, the cam sprockets are not sharp and I don't see any wear; the upper and tensioning guides are a uniform, medium-dark cramel color, not cracked. This afternoon I am removing the radiator to gain better access to bar the engine around to check timing. Then I will move the ps pump and alternator, and start planning how I am going to get the guide pins out without the slide hammer.
I am nervous about how much I have had to remove to get the cam covers off, but that's just because I am an amateur; the new cam cover gaskets will alleviate a small oil leak on the passenger side, though. I finally had to remove all the injectors in their holders, in order to get the air hoses off; in retrospect I would have had to break them to get the hoses off, as they are very stiff. I was appalled at the grit and detritus in the area where the injectors were; I greased my finger and got as much out as I could without making things worse, then wiped the bores out with clean paper towels, then stuffed some in each bore to keep grit and misc. dropped bolts out. I see no mention in the factory manual about the need to release the tensioner prior to replacing the guides, so I think I'll leave it alone and replace the chain and tensioner at a later time, if the chain stretch checks out reasonable. I have plastic parts for the cam oiler tubes, so I might as well replace these at this time.
More later; regards to all.
PS: rather than remove the radiator, I removed the fan and gained adequate access to bar the engine; set 'er on TDC #1 and removed distributor. Alas, there is no timing mark on the cam sprockets; on the left-hand (driver's) side, on the backside of the sprocket, some markings line up with the mark on the bearing tower: the marks are a "116" and below it, and "N" (may have no significance). I removed the power steering pump and bracket, and sprayed the pins with WD-40. Now, I have to develop a way to get them out.
RCR

You can pull them out with a bolt and some hardened washers. You need some with a hole bigger than the pin on the head side, and a smaller on the bolt side. Be sure that the bolt threads into the pin at least 4 turns. Turn the bolt so that the pin comes out about 1/8" and then add another washer. Be sure not to bottom the bolt out in the pin.

On at least one of the pins, you need a half washer on the head to keep it pulling straight - you will see what I mean.

The timing marks on the cam are a notch in the thrust washer and a mark on the bearing tower - behind the sprocket.

IMO, you are crazy not to do the tensioner and chain while you have everything apart. It is not a big deal.

A couple of other things - suggest new seals on the injectors when they go back in. When you start the engine, pull the lead from the ignitiion control unit and crank the engine in 10 second bursts. Then plug the lead back in and start 'er up.

And, pulling the plugs will make the engine much easier to turn.

__________________
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

Hi, thanks for the suggestion; confirms my prelim plan; glad to be reassured I won't cave in the side of the head by pulling the pins this way. Inexperience is a frightening thing; I am confronting a lot of fears in this job; sorta like performing surgery on a family member must be.
I did find the cam timing marks, on the right cam, of course. I am not far off; I stopped barring the engine a hair short of tdc, and the marks are a hair from lining up. I agree with your suggestion about the chain and tensioner; I am ordering them; also the injector seals (I already have a set). I don't have a spring compressor (to get the right-side rocker arms out). I also am ordering some tune-up parts for inside the distributor, and plan to replace the short hose behind the thermostat. What do you think about the tensioner rail? From what I can see of mine, there aren't even any grooves worn on it, nor on the other three guides, for that matter. All plastic guides are an even caramel color. Engine seems clean inside: althought there is a caramel to dark caramel colored deposit on many of the surfaces, there is absolutely no sludge or similar buildup anywhere.Updates later!

At that mileage, I would definitely do in addition, at the very least, the tensioner. It isn't difficult, not really very expensive, low risk if you follow the directions exactly, and I know that mine at ~83K was not nearly as strong as my new one. Interesting that you have no grooves on your tensioner arm. I did.

I'm not sure that color is indicative of the condition of the plastic; I cut open one of my old guides and it was actually not just a surface discoloration. My guess is that nylon (which actually contains water) dries out and oil replaces the water. But I still think that inadequate chain tension due to a weak chain tensioner will eventually break any plastic guide, old or new.

I did this job successfully, and I am definitely not a mechanic, nor do I claim to be one. But I will say that it is very important to do this job by the book, especially if you are not experienced. I know how you feel. It was like doing brain surgery on a family member. But, hey, who do you trust the most? Yourself!

Did you look at the tool rental section for the tools. I'm thinking of putting mine up there, because I'm not going to use them for at least 9 months - when I plan to get another car in addition to this one!

__________________
86 560SL
With homebrew first gear start!
85 380SL
Daily Driver Project

http://juliepalooza.8m.com/sl/mercedes.htm

The tensioner rail is up to you. I usually do it because it comes as part of a set from my supplier.

You can do this! Good luck.

__________________
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