How should machined surfaces on a cylinder block be measured for flatness?

Measuring machined surfaces on a cylinder block for flatness is crucial for ensuring proper sealing and performance in an engine. The method that involves using a straightedge and feeler gauge is the appropriate choice for this task as it allows for a practical assessment of surface irregularities.

When using a straightedge, it is placed across the surface of the cylinder block. A feeler gauge is then inserted between the straightedge and the surface in various spots to determine if there are gaps, indicating deviations in flatness. This approach is widely accepted in automotive repair and maintenance because it is straightforward, cost-effective, and provides immediate feedback regarding the surface's uniformity.

In contrast, while an electronic caliper is useful for measuring dimensions, it does not effectively measure flatness, as it lacks the necessary capabilities to detect surface deviations. A surface plate and dial indicator provide a more precise measurement, but this method is typically used in a machine shop setting rather than typical automotive practices. A laser level can assist in determining if a surface is level, but it does not directly measure flatness in the same comprehensive manner that a straightedge and feeler gauge do.

Therefore, the use of a straightedge paired with feeler blades is the most practical and widely