When pistons are ground to an oval shape for small engine designs, what are they called?

Cam-ground pistons are designed with an oval shape to reduce friction and improve performance in small engines. The concept behind cam-ground pistons is to allow the piston to maintain a tighter fit against the cylinder wall while still enabling smooth movement.

When the pistons are in a circular shape, they can create unwanted friction and wear as they move up and down within the cylinder. By incorporating an oval or cam-ground design, these pistons can expand when they reach their operating temperature, which optimizes the fit and minimizes drag during operation. This provides better efficiency and increases the engine's overall performance.

The other options do not accurately describe this specific design feature. Round pistons maintain a regular circular shape without any modifications, while flat pistons refer to a different type of piston geometry that doesn't involve the oval contours. Conical pistons are also not a standard term or design used in this context and do not imply the benefits of a cam-ground feature.