Don,

Here is a quote from Benzmac:

"...you could check by lining up the marks on the cam by turning the crank clockwise then reading the degree marks on the crank."

I think the rule of thumb for replacement is about 3 or 4 degrees...some say 5 degrees. If you do a search, and put in "timing chain" as the subject, you'll be rewarded with a host of good info.

__________________
Matt
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1995 E300 Diesel (Die Blau Frau)