What two tools are commonly used to measure valve clearance (lash) in a marine diesel engine?

• A. Feeler gauge and micrometer.
• B. Feeler gauge or laser micrometer.
• C. Torque wrench and caliper.
• D. Dial indicator and thermometer.

Answer: (B)

Measuring valve clearance relies on detecting the small gap between the valve stem and its actuation point with precision. The classic, quick method uses a feeler gauge—a set of blades with known thickness that you slide into the gap until you find the blade that fits with the proper amount of drag. This gives an immediate, field-friendly reading that matches the standard lash spec.

For higher precision or in tight spaces, a laser micrometer is used. It measures distance without contact, providing very accurate gap values and helping verify lash to tight tolerances, which is especially valuable in meticulous maintenance or production settings.

The other tools aren’t typical for valve lash measurement. A micrometer isn’t well suited to reach and measure the relatively small, recessed valve-gap directly. A torque wrench and caliper don’t measure the gap itself, and a dial indicator with a thermometer introduces a combination of measurement and irrelevant temperature data, not a direct lash reading.