herea pic of the head from the 172 engine I am stripping for the turbo build.
this head is ALREADY showing signs of BAD pre-ignition which can often lead to detonation.
the pits in the squish area of the chamber are NOT caused by debris.. these are caused by tiny explosions.. they are infact mini craters...
the piston (this is on no. 3 pot) shows exact corresponding marks..
left for much longer and the piston could well have been holed !..
The car the engine came from (Mk1 172) had 8k on the clock.. and an induction kit...
if you get an induction kit.. make sure its not running lean at top end WOT !!!.
Nick Hill - Hill Power, has the only kit and mods to sort this afaik..
Joe - ps, tell him I sent ya lol..