Of all the issues i've had with the engine (M111) misfire has been a persistent issue. I decided to investigate what i thought was a cam chain rattle. Foolishly i didn't follow procedure removing the tensioner and upon replacement it skipped a tooth. This forced me to retime the engine, and what i found along the way was shocking. Firstly, thankfully, there was no damage to the valve train but i found it impossible to time the engine to the book spec. Basically crank set at 20 deg and the locating pegs in the cams. In reality the chain had stretched to such a degree that the inlet was timing at 30deg and the exhaust 35deg, right on the limit that WIS suggests is acceptable. It's regarded that the M111 engine is very robust and cam chains rarely fail, but they do stretch and they stretch a lot, what don't know is the ramifications of this, but misfire keeps cropping up. I watched a fella check the timing on an old SL500 and found one bank 17deg out to the other bank, it ran perfectly well but clearly wasn't as smooth as it should be, but it ran. I've now resigned myself to having to change the cam chain, which is a pig of a job whichever way you do it. Anybody got any thoughts about this?