How did I break my engine?

[mojorider]

Just had a rebuild due to huge oil usage. When the engine was opened up found one of the pistons had started to break apart on the edge, it covered about 1/3rd of the piston edge and had worn down to the rings.

I can not figure out how this happened or how the broken bits got out of the engine without a trace or any other damage.

Any ideas so it does not happen again?

[simpo two]

There was a thread uncannily like this about a month ago...

[Boosted LS1]

Is it a piston with a thermal slot behind the oil control ring? If so they can crack due to very high cylinder presures (could be caused by the cam or very high compression). If the piston is all pitted and plain horrible it would be massively high pressures due to detonation.

[Chuggaboom]

Possibly just a material defect.

I bet they cast rather than forged pistons...Y/N ?

Oh and what colour were the spark plugs when removed ?