Crankshaft journals should be measured for:

Crankshaft journals should be measured for diameter, out-of-roundness, and taper to ensure they are within the specified tolerances for proper engine operation.

Measuring the diameter is crucial as it determines if the journals are still within the manufacturer's specifications. If the diameter is worn or out of specification, it can lead to insufficient oil clearance, which may result in increased wear and potential engine failure.

Assessing out-of-roundness is essential because the crankshaft must have a perfectly round journal to maintain the correct function of the bearings and prevent uneven wear. If the journal is not round, it can create excessive friction or lead to premature bearing failure.

Taper is measured to check for any variations in the journal's thickness along its length. If a journal has excessive taper, it can lead to similar issues as out-of-roundness, cause uneven contact with the bearing, and increase wear rates.

By measuring all three attributes—diameter, out-of-roundness, and taper—technicians can assess the condition of the crankshaft appropriately and determine if it needs to be repaired or replaced. This comprehensive approach helps ensure the reliability and longevity of the engine.