What's funny bout that is Salter (salter racing, the guy does great motors with decades of research behind him) did run a knurled piston in a car out of necessity (in the way back times when you couldn't get custom pistons overnight) and made 8 HP.. after 250 miles (or laps) the knurling was basically gone and the piston was rocking so bad in the bore that oil was getting into the combustion chamber...