Tolerance Added To Valve Clearance Specifications

All Caterpillar Engines

Description of Change: A tolerance of plus or minus .003″ (0.08 mm) has been added to all engine valve clearance specifications for Caterpillar engines in all applications. The new tolerance does not change the basic clearance specifications or the intervals to check the clearance, but will extend the period of time before adjustment is needed. When the serviceman checks the valve clearance, no adjustment is necessary unless it has changed more than .003″ (0.08 mm). Since valve clearance adjustment is a maintenance service, and is not under warranty, the result will be lower maintenance costs for the customer.

As an example of the new specification, the valve clearance for 3306 Engines is .015 ± .003″ (0.38 ± 0.08 mm) for inlet valves and .025 ± .003″ (0.64 ± 0.08 mm) for exhaust valves. With this specification, no adjustment of the inlet valve clearance is needed unless it measures less than .012″ (0.30 mm) or more than .018″ (0.46 mm). Similarly, no adjustment of the exhaust valve clearance is needed unless it measures less than .022″ (0.56 mm) or more than .028″ (0.71 mm).

Adaptable To: All Caterpillar engines in all applications. Service Manuals and other publications will be changed to show the new tolerance when revisions are made.

Publication Date -18/01/1978

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