I believe, unless it just flew off a sprocket, that my son has a broken timing chain on his '69 220. We did pull the valve cover and sure enough the chain and camshaft just sit there when the engine is turned.

I have read that it is possible to replace an existing chain by grinding off an existing rivet and connecting the new chain to the old and threading it up through the engine by turning the crankshaft while keeping tension on the old one you're pulling out. Makes perfect sense, but I what does one do when the chain has broken at the bottom (i.e. crankshaft pulley), is there still a way to use a shortcut here or are we into a major repair?

We will without a doubt replace the tensioner (undoubtably the ultimate cause of this promblem) as well. This looks straight forward but we would appreciate any advice.

I have two manuals but neither explain precisley what and how the correct timing is set when installing a new chain. I see a white mark on the camshaft pulley that I would assume lines up with the mark on the housing, but what about the crankshaft position? Advice here would also be greatly appreciated.

Thanks!

Better drop the oil pan and have a look-see inside there. What RPM did the chain break at? You could also have bent valves, so pull the head. Either way, you won't get out easy

As far as rolling a new chain in, you do grind the ends of the link "shafts" off, slide the link off, open up a space to connect the new chain in, put a master link in and roll the new chain through, also be sure your timing is still correct once the new chain is in. Some of the chains will come with a long "c" clip to slide over the link once the new chain is in place, others come with two small "e" clips, which I personally do not like. Always put the clip on at the back side of the chain, that way there's less chance of any intereference anywhere.

__________________
Regards,
Aaron

Aaron, thanks for your reply. The chain actually broke about 15-20 seconds after start up in which the car had not even had a chance to come up to full idle. Then it simply died with no unusual noises. We will pull the oil pan to check things out. If everything is clear will it be necessary to pull everything off the front of the engine to replace the chain?

Phil,

If everything looks ok, and you are not going to pull the head, you can roll the new chain in from the top. I can't remember on the 220 if part of the oil pan bolts may be covered by any ancillary equipment on the front of the engine, but I think you should be fine without having to remove anything. Just clear room enough at the front so you can get a breaker bar and socket on the crank bolt to turn the engine over with.

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Regards,
Aaron

Aaron,

Forgive me for being dumb, but when the chain breaks at the bottom end of the engine how does the chain get fed back up to the cam sprocket. I can see that gravity is on my side going down but not comming back up from the bottom of the crankshaft sprocket. Are you saying that while I have the oil pan off I can feed the new chain back up past the tensioner and up to the cam spocket? and if so how do I know if I am going through the guides correctly?

Phil,

Hmm, ok without getting into involved disassembly, I suppose if you were to connect the new chain down at the bottom and run some sort of wire tool down the guide, you may be able to pull it up through there, but this is purely a visualization off the top of my head. This one could be tricky!

If you are interested, I do have a 220 engine out of a '73 model. It ran great when I pulled it (the car was too rusty to be driven anymore), but I have pulled the carb (Stromberg 175) to use on a friend's MG. You can have the engine for $150 + freight or else come pick it up.

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Regards,
Aaron

Well that is the sort of direction I was heading, I just have'nt looked at this situation yet in complete detail to know if I can even see down in there enough to get away with it. As far as your engine is concerned, I sure would like to not have to replace the engine as a result of this but I'll let you know! Thanks for your help!

Phil,
A general note.
I think it would be unwise not to pull the head. Regardless of engine speed, when a chain breaks the cam(s) stop moving while the pistons do not. When this happens you can be sure, some parts are going to touch to some degree.

I tried the approach that because the car was just idling into a parking spot, there probably wasn't alot of damage, and I could just change the chain and sproket. It just doesn't happen. I even managed to get the engine restarted (not well) with severely bent pushrods and 4 bent valves.

Bite the bullet and either pull it all apart or drop in an engine like Aaron is offering. You could spend that money many times over trying to do the least amount of repair.

My $0.02. ($0.0315 canadian)

Mark

For some reason the timing chain is not detailed for the 220 on the CD, but I assume it is like the 280 single cam.

The chain runs over the cam sprocket, under the idler, over the distributor sprocket, around the crank, and up and under the tensioner sprocket. To not turn the cam, it must have broken near the crank. If you can catch the end in the pan you might be able to attatch an new chain and pull it around by turning the engine, then put the new link in from underneath. Not exactly per the manual, but it might work. I think you could go in either direction, but clockwise is preferred.

You would want to remove the rocker arms so that the valves stay closed.

Once you have a chain on, you would bring the engine to TDC on #1, remove the cam sprocket and turn the cam to the correct position and check the marks on the cam sprocket.

If you can't catch the end of the chain, then it is a fair amount of work to do the chain - probably easier to take Aaron up on his offer especially since you will always have a lingering doubt about the valves hitting a piston.

Good luck.

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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

Thanks for the info Chuck. I've got to tell ya that after sleeping on what Mark said we will live by the fix it once and fix it right rule and go ahead and pull the head. It will be a learning experience for my 16 yr. old, who is sick about this, and will hopefully restore piece of mind. One problem we now face is finding a repair manual that is more concise that the small chilton we have. For instance the section on head removal is only a few paragraphs long. I'm a fairly good shadetree mechanic, but there has got to be more to this job than that. Due to your comment about the lack of info on the CD I am somewhat discouraged. I have read all of the search posts with still no more info. I am a visual person so some exploded views with explaination would be helpful. Anybody have any online resources or links we might check out?

If you send me an email (ctaylor738@aol.com), I will send you by return what I could find on the CD - a section on replacing the slide rails and one on the rocker arms. Includes some diagrams. It will be helpful.

Also suggest you try www.tmcpubl.com for a "parts list" for your car. These have great exploded diagrams of everything and I find them helpful.

Lastly, you might get the Haynes manual for the 230-280 SOHC. I can't believe the 220 is all that different.

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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