On my 4.5, I changed my chain at ~140k miles. It had a massive 12° of stretch, but no interference between the valves and pistons occured. I don't know if the 5.0 and 5.6 M117's are this way, but it's very possibly because the pistons on a 4.5 don't go all the way to the top of the block - they do on a 3.5 M116, and I am pretty sure they do on a 3.8 and 4.2 M116 as well. Timing chain stretch on these is more likely to cause the valves to kiss the pistons. See the link in Hatt's thread? Looks like an M117...

I saw a nice 420SEL in the junkyard. Well, it would have been nice had the owner replaced the guide rails. I saw 175k on the odometer. I grabbed the starter from it, and the valve covers were already off showing the valvetrain someone probably wanted. Several bent valves on the right side of the engine (didn't check the left). It was saddening how a $25 job (in parts) cost this car its life.

I almost bought an 87 420 for $2500. It was immaculate, 120k miles. And I mean IMMACULATE. Someone else got to it before me and offered $3k. I was going to offer back with $3k but it was gone. 420s are pretty low demand, people prefer the more powerful 560 with its nicer trim (IMO). Price is a bit high, you can get a perfect 560 for that.

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Back in the saddle - 1972 280SE 4.5