<VV> (extreme motor failure) long sad learning curve story.

[Robert Marlow]

My theory, Tim, based on the same skepticism expressed by Matt and Dennis:

Because this engine was, as you noted, "in the process of having 
valves adjusted, carbs tweaked etc.," I think that he had the 
throttle linkage disconnected when he turned the key.  It fired, went 
to instant WOT with no load, and blooey.  When it blew and got quiet, 
he tried to crank it again, which is how the starter nose broke.

I do speak from some experience.  I once cranked an engine without 
having remembered to re-attach the throttle linkage, and wowser did 
it take off.  Fortunately, I was fully seated in the drivers seat 
when I did this, so I was able to shut it off almost instantly and no 
damage was done.  The engine runs and drives to this day.  I was 
lucky.  Your friend was not.

--Bob