How should readings for cylinder out-of-roundness be taken?

Readings for cylinder out-of-roundness should be taken at two points, 90 degrees to each other because this method ensures a more accurate assessment of the cylinder's shape. Measuring at 90-degree angles allows for the identification of any distortions or oval shapes that may not be detected when measurements are taken in a single direction or at random angles. This technique provides a comprehensive view of the cylinder's geometry, which is critical for maintaining engine performance and preventing issues related to improper sealing and oil consumption.

Other approaches, such as measuring at random angles or only at the top or around the skirt of the cylinder, would limit the ability to detect potential problems comprehensively. These methods could miss important variances in the cylinder's dimensions, leading to incomplete evaluations and possible engine performance issues.