If your talking about the type of specs I think you are, its probally a little detonation, alltough thats normal wear sometimes.
Niether the piston or the head are really made of strong materials. Pretty soft stuff. Most engines with 9+ gallons of racing that I've seen have had some specs on the piston or head.
What engine, fuel, glow plug, carb insert are you running? What heads shims? Stock? What car? Pipe? Clutch setup?
Maybe its someting obviously mismatched?