Final answer:
Cracks in pistons are most likely to be found at high-stress points such as the piston pin holes, skirt area, and ring lands. Piston cracks, like mud cracks, often start small in stress concentration areas and become more visible as they spread, but are not used as way-up indicators.
Step-by-step explanation:
When inspecting a piston from an engine, cracks are most likely to be found in the areas subjected to the highest stress, such as around the piston pin holes, the skirt area, and the ring lands. The piston pin holes are under constant stress as they connect the piston to the connecting rod. The skirt area is prone to cracking because of the side forces exerted upon it during operation. Finally, cracks may also be found in the ring lands, which are the grooves that hold the piston rings, due to the high pressure and temperature fluctuations these areas endure.
It's interesting to note that, similar to mud cracks, which are typically wider at the top and narrow towards the bottom, piston cracks may also start small within the stress concentration areas and become more visible as they spread to the surface. However, unlike the mud cracks mentioned, piston crack inspections do not typically utilize them as way-up indicators. Instead, inspections focus on identifying potential structural integrity issues that could result in engine failure.