Well timing chains are a complicated issue, do a search.

But the M116 V8 in the 420's you would be crazy not to do the chain at 100k, or every 10 years. Why because they are long with weak plastic guides, the guides get hard and will snap. A rebuilt engine is $6k-$8k.

Now the M117 in your 560 is stronger, but 120k is pushing it. You could probably push it to 150k though.

If it were my car I would just change the guides and chain and be done with it. But I could do it myself in a day for a couple hundred bucks.

If you are buying one and the owner says he doesn't know, that means no. Plan on changing the chain unless you have paper proof of it being done.

The M117's also seem to wear their cams kind of fast.

The valve stem seals do go bad and you will burn oil when they do.

This was an $70k new so it will require more maintaince then cheaper cars. MB are not low maintaince cars that is a myth.

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2016 Corvette Stingray 2LT
1969 280SE
2023 Ram 1500
2007 Tiara 3200