ORIGINAL: ChuckAuger
And if Dave HAD sucked a HANDFUL of dirt down his intake, I would expect the soft aluminum piston to wear much faster than the ostensibly harder nickle liner. Isn't that the whole reason to make the liner harder and the piston softer??
Not necesarilly true.
In engineering, when you want to lap a bore, you use a soft rod (such as aluminum) as the lapping rod for a very good reason. The hard abrasive particles will become embedded in the soft alloy and then perform their wearing action against the bore as the lapping rod is moved.
Once a sharp, hard, abrasive particle becomes embedded in the soft alloy of an aluminum piston, it won't actually cause any wear on that piston -- because it stops moving relative to that piece of metal. It will wear the bore however because it's sliding up and down with every rotation of the engine.