The holes on the side of some pistons are flat-out nasty. Some might wonder, how could the side of a piston be scorched so badly? There are a few reasons why pistons get destroyed. A scuffed skirt (the side of the piston) is usually an indication of insufficient oiling. Lifted ring landings (most of the time) are attributed to an overly rich fuel condition. The fuel gets down on the side of the piston and combusts there on the next engine cycle. That lifts the ring land, which in turn pinches the second ring and allows oil to pass through to the top of the piston. Once the oil gets mixed with the air and fuel, all hell breaks lose. The oil will cause major detonation, and then kaboom! You now have a torched piston.
Another fact about lifted rings lands is that when the fuel gets down on the side of the piston, it hydraulics the ring land, which then sets in motion the aforementioned events that lead to oil on top of the piston and a nicely torched slug. The overly rich condition is perhaps the most popular reason for lifted ring lands.
Piston destruction can also be due to super-lean conditions, usually caused by too much timing (either from low octane or too high for the given cylinder pressure), not enough fuel volume, or a combination of both. The cylinder gets too hot and the combustion process produces a torch-like effect that completely tears up the piston, cylinder head, and even sometimes the block. Torching the block would be the worst of it all. Extreme lean conditions aren’t always tuning related. I’ve seen my fair share of failed fuel pumps, broken ignition systems, dead fuel injectors, etc. cause that very problem.