I replied once to this thread and it doesn't seem to have shown up, sorry if it happens twice.
Thanks much Klaus & guys for the good information on my head. This list is just a great resource!
I took the car to another wrench and was really impressed with him--Rob, the owner of Benz Frienz here in Seattle. His guys are a friendly bunch too, they're all hard-working genuine vintage Mercedes enthusiasts with no bulls*@t allowed, so the gold chain set need not apply.
Benz Frienz is the coolest operation, tucked away in an old Seattle neighborhood, Rob's been there for 20-something years. Lots of great old Benzes there. He has forgotten more than most of us will ever know about these vintage Benzes. He took mine out for a diagnostic ride and came back with new information. He ran the car with one plug lead loose on each consecutive cylinder until, on #6 (the cyl. with a 140psi compression reading), the pinging was reduced by 95% with that plug lead loose and putting the engine under load. He thought that it was not 'pinging', but some kind of mechanical sound, like a loose valve seat, etc.. The 195psi compression reading is on cyl. #1, so that tends to confirm that it is not an excessive compression detonation/pinging noise, but something else.
So, he's busy now, but week after next I'll be taking the car down for Rob's ministrations. I'm keeping my fingers crossed that the head hasn't been shaved too much and that whatever is wrong with the head can be fixed, if the problem is in the head.
The compression numbers range from 195psi to 130psi, 40% dry to 10% wet, which still sounds ominous.....might be ending up with a rebuild anyhow.
Regards,
Will