I'm guessing this pic was taken with the valve spring in place and somehow compressed... and that no measurement of the valve stem and guide bore was taken...
I'd like to be wrong in that assumption.
If my guess is right, then it would be difficult to feel the slop in the clearance, etc.
It would be a drag to carry on with a worn valve stem & guide till the valve head separates, noisily beating the piston to death, AMHIK.
but then again it may be fine till the next inspection.
in the pic, that little bit of valve seat looks sort of recessed... but maybe the image is misleading.
my best guess is bmwrench has it right.
The cylinders on my old /5 were so tapered we went from standard to 2nd over, though that engine was running pretty well before I tore it down for head work.
(not the same engine that swallowed a valve).
Originally Posted by khale
Exhaust valve open.