What should be done when the depth of a cylinder block liner counterbore varies 0.003" in four places?

When the depth of a cylinder block liner counterbore varies by 0.003" in four different locations, it indicates that there is inconsistency in the surface, which can lead to problems with the sealing and overall performance of the liner. It is crucial for the liners to be seated evenly to ensure proper compression and prevent leaks.

Machining the counterbore to achieve a consistent depth is the proper approach. This process involves precisely removing material from the counterbore to ensure that all depths match, thus allowing the liners to be installed uniformly. Additionally, shimming can be done if needed to make small adjustments, ensuring that the liner heights are equal once installed.

This solution not only addresses the problem of uneven counterbore depth but also helps maintain the integrity and performance of the engine. Consistency in liner seating is vital for optimal engine function, longevity, and performance.