I have had that vapor lock (I think) happen in a 1967 172 leveling off
after a long climb to about 8500 ft. It was dead smooth air during
the climb. We were speculating that maybe the under-the-floor temps
are high and if the coordination happened to be such that the fuel
flow went to near zero for an extended time in one of the tank lines
to the fuel selector. We had forgotten to switch from both to one
tank above 5 thou.

I understand Cessna had a hard time duplicating the problem after from
the few field reports that came in before the AD was issued. They
never published a reason for it as far as I know.

There was a total power interruption for maybe 20 seconds while the
two of us (both engineers) franticly tried to figure out what was
happening while we were over northern Wisconsin near night. The last
thing was pulling the fuel quick drain although I don't know if that
was the fix or if the problem corrected itself via other means. It
definitely was a fuel starve out type failure and not a flooded out
type of failure. We most certainly were leaning for the climb at
that altitude. We had EGT and we always monitored it.

Has anyone else encountered this stumble? Could it really happen to
be the dead smooth air and the coordination?