Piston numbering is typically done from the timing chain side of the engine. However, there's no single universally standardized way to number them across all engines. While it's *likely* that the number 1 piston is closest to the timing chain, the only definitive way to be certain is to consult a factory service manual or a detailed diagram for that specific engine. You can use the firing order in conjunction with a diagram to determine each piston's number.
