Check the timing chain for stretch, and check the chain guides to see if the plastic is old and brittle.
Timing chains, guides, and tensioners are recommended to be replaced every 100,000 - 120,000 miles.
Do a search on any of the above topics. The board is full of great info.
2001 E430, Bourdeaux Red, Oyster interior.
1973 280SE 4.5, 170,000 miles. 568 Signal Red, Black MB Tex. "The Red Baron".