No spec listed because you replace the chain if a 6 degree offset key won't restore it. MB manuals are a bit thin on "normal mechanics" because German mechanics already know all this, they aren't OJT over there!

Chain stretch measured by aligning the mark on the cam tower with the notch in the thrust washer on the cam sprocket and reading the crank degree wheel must not exceed 8 degrees -- if it gets as high as 12, the valves will touch the pistons.

If more than 8 degrees late by the valve lift method (as described in the manuals), you cannot correct with the 6 degree offset, so you replace the chain -- not stated because you are suppsed to know it, I guess!

If you have a single row chain on the 380s, check every oil change for safety, they are a bit frail. The double row replacement is as good as the one in the 420, but it's a bit iffy, check at least every 30,000 miles.

Peter

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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!