2012/10/03 Caterpillar

Caterpillar Products: Machine Engines

All 3500 Series

Correct valve lash settings help provide the following benefits:

• Optimum performance

• Economical fuel consumption

• Contributes to maximizing the service life of related parts

• Maintaining 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.

A minor error in the valve lash setting may not cause immediate damage. However, the error will contribute to reduced performance and fuel economy.

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 in order to do the same amount of work.

Inspect the valve lash and adjust the valve lash according to the Operation and Maintenance Manual, "Maintenance Interval Schedule".

For instructions for measuring the valve lash and setting the valve lash, refer to the engine Testing and Adjusting.