When Do I Need to Adjust the Valves on My New Engine?

Engine Intake and Exhaust valves should be adjusted at the first oil change on a new engine. For Cat^® Marine Engines, the first oil change could be recommended at 250, 500 or 1,000 hours, depending upon configuration. Consult your manual for specific configurations and intervals.

Correct valve lash settings help provide the following benefits:

• Optimum performance
• Maintain fuel consumption
• Contribute to maximizing the service life of related parts
• Sustain rated exhaust emissions

Valve recession occurs normally due to engine operation. Valve recession decreases the valve lash setting, which makes initial and regular scheduled maintenance of the setting necessary.

Incorrect valve lash setting can cause the following conditions:

• Excessive valve lash causes the valves to seat at higher velocities that can exceed the design capabilities of the valves, resulting in broken valves.
• Insufficient valve lash can prevent the valves from seating. Possible results are burnt valves and contact of the valves with pistons.
• Insufficient exhaust valve lash opens the valve prior to completion of the power stroke. Some of the combustion occurs in the exhaust system instead of the combustion chamber. Cylinder pressure is reduced, resulting in a loss of power and boost.
• Because of reduced power and boost, the operator may increase the throttle, which increases fuel consumption to do the same amount of work.

A valve lash adjustment is critical because the valves of a diesel engine play a key role in the combustion process. Specifically, the intake valves control the flow of air entering the cylinder, while the exhaust valve controls the flow of exhaust gases exiting the cylinder. Both inlet and exhaust valves must close and seal completely during the combustion process.