Bill Freeman wrote:

I've seen several detonation failed pistons (at unlimited
air races) that burned down the side of the piston and
eventually opened up a hole thru the side/top "corner"
into the crankcase.  Left the rings intact, sort of bridges over
the gap where the aluminum was burned away.
Always suspect detonation induced failure
when there is a non-mechanically-caused  (dropped
valve, piston just broke in half,etc) piston hole.
You'll be right  if there is a smooth-edged hole without
other mechanical damage.  Happens all the time.

Bill

 
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