I pulled the valve cover in a light drizzle this afternoon after getting
the Yellow Peril's overaxle pipe back on to stay (Had to buy a pipe expander)
and replacing an actuating pin in the driver's doorhandle. So then we decided
to see what was what. Found that the engine does NOT turn 270°, actually it is
less than 180°. Seemed odd. So we pulled the valve cover and at first glance
it looked OK but then I looked all the way back and found a valve spring in 3
pieces, ONE keeper, the spring out of the valve stem seal and a few other
pieces of metal not immediately identifiable. It was the 11th valve counting
from the front, the #6 intake valve, NOT in evidence. Must be in the cylinder.
I believe it must have fallen out when the engine was not running. Will have
more info when I pull the head.

One thing that concerns me is that it looks like the rocker arm was trying to
push that valve too far open. I do have two collapsed hydraulic Chevy lifters
in there that I got when I replaced a defective cam in Panama. I had shimmed
them to the same height as solid lifters and took all the hydraulic stuff out
of them. It will be interesting to see if one of those came apart or if not,
what was the cause of this event.

Many thanks to all of you who guessed with me. This is the first time in
almost 40 years of working on Volvos that I have had this particular problem.
I have extra valves, seals, springs, etc. so at this point it does not seem
to be the disaster I had anticipated.
--
George Downs Bartlesville, Heart of the USA!