DIESEL MAIN BEARING BOLT HOLE THREAD PITCH CHANGE PROCEDURE

Main bearing bolt hole thread pitch for number 2 and 3 main bearings have been changed from 1.75mm to 1.76mm on V6 diesel engines. The main bearing bolt has not changed. This results in an interference fit with the last few threads when the bolt is screwed into the hole. This interference spreads the load throughout the bulkhead rather than concentrating it at the surface. Engine blocks that have a main bearing bolt hole pitch of 1.76mm for number 2 and 3 main bearings are identified by a stamped letter "G" behind the cast part number. The cast part number is located on the top rear of the block next to the oil pump drive assembly. When installing these bolts it is essential that engine oil be applied to the threads to prevent galling. It is normal for the bolt to tighten up slightly during the last few turns upon installation. Do not attempt to "clean up" number 2 and 3 main bearings block threads by retapping with standard tap size M12-1.75. The M12-1.76 tap used is not a standard tap size.

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