Posted for "George Braly" <gwbraly@gami.com>:

 Craig,
 
 I have actually captured a “pure pre-ignition”  event data stream on the test
stand.  Internal cylinder pressure data (50Ksps).
 
 The engine had a helicoil tang that would reliably go into pre-ignition at
about 70% power with the CHT above 420dF.
 
 We played with it - - teasing it for a while into and out of pre-ignition.
  Then the spark plug departed the engine.
 
 Whoops!
 
 Regards,  George

""""
 Scott:
 He has de-constructed one or more pistons in the prior engine - detonation
was the culprit.
 
 Amazingly, probably not! We have watched many detonation events--some even
heavy detonation events--some for extended periods-without any ill effects on
the piston, cylinder or engine in general. The danger is these turning into
pre-ignition, usually from a damaged spark plug from the detonation. That can
destroy the engine in 30 seconds and while our observations are that
detonation doesn't hole a piston, pre-ignition will do it in a heartbeat.
 Detonation gets blamed for a lot for which it is completely innocent! <g>
 Walter
""""