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  #16  
Old 01-01-2007, 06:19 AM
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I got strange chain stretch readings too

About a couple of months ago I attempted to check chain wear using the same proceedure, but also could not get consistent measurements. Using the dial indicator method I got 17 degrees BTDC and with the cam mark alignment method I got 5 -6 degrees ATDC. I tried to do the dial indicator method several times and got the same answer, which I could not explain. My vehicle has camshaft code 11, which I could find no information on, so I basically gave up on the woodruff key fix.

Given the simple timing mark measurement indicated wear near Mercedes wear tolerance limits, I decided to just go ahead and install a new chain. I have a new chain and will be installing it later this week, most likely. This is on my 1985 300SD Turbo Diesel. This car has O.K. power, that I am hoping will be greatly improved by replacing the chain, readjusting the valves and doing the IP timing.

My brother owned a 1983 300SD for about 2 weeks (decided to do some quick repairs and sell, because he wanted a vehicle with a little nicer interior) that he no longer has as of a few weeks ago. We did the chain stretch measurement on this vehicle with similarly strange results. I don't recall the camshaft code for this vehicle. Given the difficulties we had trying to measure chain "stretch" on my (1985) vehicle earlier, we didn't really pay much attention to the measurement.

I read about some vehicles needing woodruff keys with rather large offsets straight from the factory, so we assumed that we both had vehicles with this issue. BTW - this 83 SD had lots of power - easy to get the wheels to chirp.

It seems like if our chains were off by one camshaft gear tooth, the vehicles would have rather serious issues in terms of power or valves hitting pistons, etc., so I don't think this is the problem, but maybe I'm wrong.

I'm not sure this helps explain anything, but I am basically confirming that you are not alone in getting inconsistent readings. I sure would like to explain what is going on.

Once I get the new chain on the 1985 300SD, I will likely do the two measurements again and see what I have. Maybe this will help resolve the issue.

If anyone has the specs for camshaft code 11 that they could post, it would be appreciated.
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  #17  
Old 01-01-2007, 09:09 AM
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Quote:
Originally Posted by Scott98 View Post
Just how much valve lash do you remove? I loosened it up a lot.
You are supposed to remove all of it. That is so that the 2mm of lift is measured from 0 cam lift... instead of wherever the cam eventually touches the valve. Back that valve off until it touches the cam, then back it off some more. Then check the stretch with the 2mm method.

-Tad
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  #18  
Old 01-01-2007, 09:11 AM
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The valve lash should be completely removed. With the cam lobe up bring the valve adjusting nut all the way to the top snuggly against the cam lobe. Don't force it just make it snug.

Another problem can be the post for the dial indicator. It really needs to be tight. There should be no movement on the post.

I had cam code 11 in my engine too. I just assumed it had the same specs as the other cams listed in the FSM.

Danny
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  #19  
Old 01-01-2007, 09:30 AM
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Removing it means tightening it up so there is no lash (space for the feeler gauge). Perhaps that's the problem you are experiencing Scott.
Steve
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  #20  
Old 01-01-2007, 11:09 AM
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Quote:
Originally Posted by Bodgit2 View Post
Removing it means tightening it up so there is no lash (space for the feeler gauge). Perhaps that's the problem you are experiencing Scott.
Steve
Bingo. I loosened it. Aargh!!!!!!!!!!!!! I will check it again later this morning and post the results.

Thanks for everyone's help.

Scott
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1982 Mercedes 240D, 4 speed, 275,000
1988 Porsche 944 Turbo S (70,000)
1987 Porsche 911 Coupe 109,000 (sold)
1998 Mercedes E300 TurboDiesel 147,000 (sold)
1985 Mercedes 300D 227,000 (totaled by inattentive driver with no insurance!)
1997 Mercedes E300 Diesel 236,000 (sold)
1995 Ducati 900SS (sold)
1987 VW Jetta GLI 157,000 (sold)
1986 Camaro 125,000 (sold - P.O.S.)
1977 Corvette L82 125,000 (sold)
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  #21  
Old 01-01-2007, 01:49 PM
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The new results are in. I checked it about 15 different times from various angles. It really is a challenge getting the indicator as straight as possible. The more of an angle its on, the more your reading will indicate "less" stretch. It looks like my previous error was most definitely the valve lash. I thought it meant to loosen it, not tighten it. I loosened up the retaining nut and then screwed the other nut up by hand until it was snug.

My new reading was 15 degrees ATDC. My 616 with #10 cam code should read 11 degrees ATDC with a used chain or 9 degrees ATDC with a new chain. I assume I should use the used chain measurement as my bench mark. Doing that, 15 - 11 = 4 degrees of chain stretch. Is that right, using the used chain figure? Or should I use the new chain figure which would give me 6 degrees (15 - 9) of stretch? Also, if I only have 4 degrees of stretch, then I probably don't need a new timing chain, or do I?

Anyway, I'm glad to report I don't have 14 degrees of chain stretch . I'm not very mechanically inclined so sometimes I make mistakes like that (valve lash). Thanks for all of the help from this forum. I would never be able to work on my car without this website.

Scott
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1982 Mercedes 240D, 4 speed, 275,000
1988 Porsche 944 Turbo S (70,000)
1987 Porsche 911 Coupe 109,000 (sold)
1998 Mercedes E300 TurboDiesel 147,000 (sold)
1985 Mercedes 300D 227,000 (totaled by inattentive driver with no insurance!)
1997 Mercedes E300 Diesel 236,000 (sold)
1995 Ducati 900SS (sold)
1987 VW Jetta GLI 157,000 (sold)
1986 Camaro 125,000 (sold - P.O.S.)
1977 Corvette L82 125,000 (sold)
1965 Pontiac GTO 15,000 restored (sold)
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  #22  
Old 01-01-2007, 03:43 PM
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Quote:
Originally Posted by Scott98 View Post
My new reading was 15 degrees ATDC. My 616 with #10 cam code should read 11 degrees ATDC with a used chain or 9 degrees ATDC with a new chain. I assume I should use the used chain measurement as my bench mark. Doing that, 15 - 11 = 4 degrees of chain stretch. Is that right, using the used chain figure? Or should I use the new chain figure which would give me 6 degrees (15 - 9) of stretch? Also, if I only have 4 degrees of stretch, then I probably don't need a new timing chain, or do I?

That's more like it. The valve lift method results in a chain elongation of 4 degrees. The cam marks also confirmed a chain elongation of 4 degrees.

No need for a new chain. If the numbers bother you, you can purchase a 4 degree Woodruff key for the camshaft which will return the cam to spot on.
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  #23  
Old 01-01-2007, 06:02 PM
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Quote:
Originally Posted by Brian Carlton View Post
That's more like it. The valve lift method results in a chain elongation of 4 degrees. The cam marks also confirmed a chain elongation of 4 degrees.

No need for a new chain. If the numbers bother you, you can purchase a 4 degree Woodruff key for the camshaft which will return the cam to spot on.
Just out of curiosity, where does the woodruff key go? Is it difficult to install?
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Scott
1982 Mercedes 240D, 4 speed, 275,000
1988 Porsche 944 Turbo S (70,000)
1987 Porsche 911 Coupe 109,000 (sold)
1998 Mercedes E300 TurboDiesel 147,000 (sold)
1985 Mercedes 300D 227,000 (totaled by inattentive driver with no insurance!)
1997 Mercedes E300 Diesel 236,000 (sold)
1995 Ducati 900SS (sold)
1987 VW Jetta GLI 157,000 (sold)
1986 Camaro 125,000 (sold - P.O.S.)
1977 Corvette L82 125,000 (sold)
1965 Pontiac GTO 15,000 restored (sold)
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  #24  
Old 01-02-2007, 09:10 AM
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The woodruf key keeps the chain sprocket from slipping on the camshaft.
Position intake #1 cam lobe straight up. (same as checking chain stretch).
Remove the tensioner spring.
Support chain sprocket to keep tension on it. I use a bungee cord.
Remove chain sprocket. Put lots of rags down you don't want anything dropping into the engine.
Remove the large thrust washer. You should now have easy access to the key.

Instalation is reverse of removal. Very easy if you take your time.

I had the same results of 4 deg off. I put a key in and it works great.

Send me your e-mail address and I'll send you a PDF file with instructions.

Danny
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  #25  
Old 01-04-2007, 05:42 PM
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I found this thread to be very helpful:

Sudden Chain Tensioner Spring Wear

Ddanny
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  #26  
Old 01-04-2007, 10:06 PM
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Quote:
Originally Posted by Scott98 View Post
and then rotated the cam until I got 2mm of lift.
Scott
I assume that you rotated the cam by turning the CRANKSHAFT bolt ?
Just in case someone read that as actually rotating the cam itself...
If you turn the cam to do this... the engine would have to not be running.. thus the oil pressure would not be going to the ratching/oil pressure operated chain slack taker upper... and that could sure mess up the measuring ....
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  #27  
Old 01-04-2007, 10:09 PM
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Quote:
Originally Posted by leathermang View Post
I assume that you rotated the cam by turning the CRANKSHAFT bolt ?
Just in case someone read that as actually rotating the cam itself...
If you turn the cam to do this... the engine would have to not be running.. thus the oil pressure would not be going to the ratching/oil pressure operated chain slack taker upper... and that could sure mess up the measuring ....
I attempted to turn the camshaft once. No way it wanted to move the crankshaft.........and I wasn't about to get a 3 foot bar to force it.......
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