CYLINDER GP-STEERING 3846751 - Caterpillar

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OFF-HIGHWAY TRACTORS
OFF-HIGHWAY TRUCKS
WHEEL LOADER
EXCAVATORS
ALL 3500 AND 3500B DIESEL INDUSTRIAL, MARINE, GENERATOR SET, LOCOMOTIVE, VEHICULAR ENGINES;
ALL CATERPILLAR MACHINES POWERED BY 3500 OR 3500B ENGINESReference: Service Magazine; January 27, 1997; Page 34; "Premachined Valve Seat Inserts And Precision Valve Guide Increase Valve Life". Engine News, February 1997, Page 12, "Premachined Valve Seat Inserts And Precision Valve Guide Increase Valve Life".Problem:
Reports indicate that some 3500 engine cylinder heads that have been rebuilt with premachined valve seat inserts and precision valve guide are having the valves and valve seats lapped or machined. Lapping or machining premachined valve seat inserts decreases valve life. Solution:
Premachined valve seat inserts and precision valve guides are specifically designed to provide the proper concentricity of the valve and valve seat. See the REFERENCE. Because the premachined valve seat insert is manufactured to the correct finished dimensions, it does not require machining/lapping after installation into the cylinder head. Machining will decrease the concentricity and proper contact between the valve and valve seat insert. This will result in decreased valve life.The premachined valve seat inserts and valves are designed so that proper seating will occur very early in the break-in after initial engine start-up. Therefore, it is very important that the valve lash and bridge lash be adjusted at the first 250 hour interval after the installation of the rebuilt cylinder head or new engine startup. Also, because proper valve seating occurs only after running, cylinder heads rebuild with premachined valve seat inserts and precision valve guides should not be bench vacuum tested for leakage.COPYRIGHT 1999 CATERPILLAR ALL RIGHTS RESERVED