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  #1  
Old 08-08-2003, 03:26 PM
sms sms is offline
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Question 560sl chain stretch measurement?

I'm in the process of replacing my guide rails and tensioner in my 560sl (117.967 engine) per Thomaspins' detailed instructions on his website. However, I'm having some intial problems. The main area of confusion is in the measuring of the chain stretch. I removed the passenger side valve cover and rotated the crankshaft until the camshaft and tower marks aligned, but when I looked on the balancer marks I was nearest to a mark that looked like this 18|0. I expected to be looking at marks that look like this 3|0 2|0 1|0 O 1|0 2|0 3|0.

What am I missing?

Thanks!
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  #2  
Old 08-08-2003, 04:24 PM
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Steve -

Take a look at this picture. Retarded is to the left of the 0 (cam tower marks aligned) facing the car, as in this example.

You can just see (this is on a 560 engine) that the numbered markings are at 10 degree intervals, with a line for the intermediate 5 degree ones.

18 degrees out (yours) is an awful lot and I cannot see how the engine would run without damage unless the crank degree wheel has slipped. Is the 18 degree reading after installation of the new chain? If so, you probably skipped a tooth.

Are you sure you took the engine through a couple of crank rotations and that the cam tower mark on the driver's side was also aligned?

You are also changing the tenioner, I assume?
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  #3  
Old 08-08-2003, 04:49 PM
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Thomaspin,

Wasn't planning on replacing the chain now since the car has only 76K miles. I just wanted to insure that I didn't break one of the rails because of brittleness or too much chain play.

I rotated the cam 4x and every time it came up at the 18 mark. I suppose the ringer on the damper could have rotated some back when I replaced the water pump last year. However, when I did that job I only loosened the damper but never fully removed it!

Steve
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  #4  
Old 08-08-2003, 05:07 PM
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Other can correct me here, but I think if you were really 18 degrees out, valves would be hitting pistons. How did you check that you replaced the degree wheel correctly?

Rails are usually a 100k job. If yours are very dark brown, you probably should replace them - the one that goes first is the one on the left of the driver's bank as you face the engine, and you will have to remove the sprocket to extricate/replace it. I illustrate this.
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  #5  
Old 08-08-2003, 05:12 PM
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Is there dirt on the timing marks? I wouldn't think that there is a mark that specifically reads "18". Maybe it is really "10"?

A little less than 10 degrees stretch would make a lot more sense.
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  #6  
Old 08-08-2003, 05:17 PM
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I think some digital pictures will help here! Will repost later today.

Thanks,

Steve
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  #7  
Old 08-08-2003, 10:00 PM
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Here are some pictures that may clear things up!





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  #8  
Old 08-09-2003, 12:17 PM
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Well, that certainly says '18'.

I think you are 180 degrees out on the crank - take the engine through a half turn until you see the myriad timing marks on the other side of the degree wheel, with the cam tower marks aligned. The '18' looks like an identification number, not a timing mark. Those s/b elsewhere on the wheel.
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  #9  
Old 08-09-2003, 01:19 PM
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If I'm at 180 deg and the engine runs ok, is there a problem?

I'm not sure, but In the process of doing this job I now have a real bonified problem! One of the (4) allen bolts that hold the alternator to the head won't come out. I've lubricated it, banged it, heated it, but nothing works. Of course, the hex is now getting beat up which makes it all the more difficult. I had the same problem when I was removing my a/c compressor. One lousy bolt in an inaccesible location. On the a/c bolt it took me a week of weeknights to get that out. I ended up drilling it out, but that was only a bracket. I'm not that brave on the cyl head!

Any suggestions on what to do with these allen head bolts?


Also, visually inspected the chain and noted that on the passenger side it was very easy to lift the chain off of the flat rail. Is that any indication of chain stretch?
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  #10  
Old 08-09-2003, 01:31 PM
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I just rotated the crank around 180 deg and sure enough I'm now at zero and the cam mark is now rotated by 90 deg. How do I interpret this?

Thanks,

Steve
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  #11  
Old 08-09-2003, 08:58 PM
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One idea on the tight allen head bolt is to punch a slightly oversize Torx bit in and loosen the whole thing with an air impact wrench, which you probably want done at the local independent shop. Indy is also likely to have lots of special 'easy out' tools to cope with this (not infrequent) problem.

Are you sure there is no chance that you rotated the degree wheel when you did the water pump job? Do you see all the degree wheel markings, similar to those in my picture?

How loose is 'loose' on the cam chain - I assume you mean on the inside of the V on the passenger side, not on the (curved rail) tensioner side? Is the tensioner holding the curved rail up tight against the chain after a few rotations (to charge it with oil/hydraulic pressure)? Did you do anything that might have made the chain jump a cog on the sprocket(s)?
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  #12  
Old 08-10-2003, 01:24 AM
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Hi,

Got the allen head bolt out by rotating the bracket at which point I applied more impact and got the bolt out.

Don't think I rotated the harmonic balancer marks since I never got the balancer off. I didn't have a puller at that time and eventhough the bolts were out I couldn't get the balancer off.


Don't both cam marks (right & left side) have to align in order for the balancer to be in the correct position?

Steve
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  #13  
Old 08-10-2003, 11:14 AM
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Yes, both cam marks must align.
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  #14  
Old 08-10-2003, 01:22 PM
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I have both cams aligned with their respective marks as well as the distributor rotor aligned with its marks on the dist. housing, but still the damper mark reads 180?

Steve
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  #15  
Old 08-10-2003, 01:40 PM
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Hi again,

I know it looks like the damper is on wrong, but I'm not sure this is possible since its keyed onto the shaft and the (6) bolts that hold it on can only be put on one way. One of the (6) holes is spaced differently from the others.

I'm thinking that perhaps the cam sprockets are on wrong since they have (2) slots for the woodruff key that are 180 deg apart?

PS. Of course, don't know why they would be 180 deg off since I don't think anybody has touched this before me.

Steve
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