Service Bulletin No. 388 C

Supersedes Service Bulletin No. 388B and Supplement No. 1 to Service Bulletin No. 388B

November 22, 2004

TIME OF COMPLIANCE

Helicopter Engines – 300 hour intervals or earlier if valve sticking suspected. All Other Engines – 400 hour intervals or earlier if valve sticking suspected until exhaust valve guides are replaced with guides made of improved material. (Refer to latest revision of Service Instruction No. 1485.)

To insure positive and trouble free valve train operation, the inspection procedure described in this publication should be accomplished as recommended in the Time of Compliance section of this publication. Failure to comply with the provisions of this publication could result in engine failure due to excessive carbon build up between the valve guide and valve stem resulting in sticking valves or; broken exhaust valves which result from excessive wear (bell-mouthing) of the exhaust valve guide.