Engine Builders: The AERA Technical Committee offers the following information regarding cylinder head service for 1998-2002 Cummins 5.9L ISB/QSB engines, also known as "24 valve" or "4 valves per cylinder" engines (current service information is found in Bulletin 366193, revision 01 published in February 1999). Previously published service information may be incorrect due to updated service information that has changed.