it was running fine no check engine light. Serviced every time through MB. I was at a light I took off, then I as I gave it gas to pass a truck next to me something gave inside the engine. puff of smoke from under the hood, pulled over, turn it off. Oil all over the ground. Towed it to Mechanic, he showed me holes in the oil pan, there was pieces of metal all over. - cpic
sounds like your balance shaft cog wore down, and chain jumped the cog, and allowed the valves to hit the pistons.
Known problem with M272 and M273 V6 and V8 engines
Mercedes manufactured thousands of these engines for world wide distribution a huge number had a poorly manufactured balance shaft sprockets, the metal wears down prematurely and allows the chain to jump off if not replaced. - gavinbr