BOLT 1992375 - Caterpillar

Introduction
The problem that is identified below does not have a known permanent solution. Until a permanent solution is known, use the solution that is identified below.Problem
A change to the casting was made to the various cylinder head groups on the C9 engine. The change was made in order to address cracking of the cylinder head along the oil rail. The oil rail supplies high pressure oil to the injectors. A new plug for the end of the rail was introduced. the new part number is 271-7442 Plug . There was not a change in the part number for the new cylinder heads. Some of the Parts Identification manuals are incorrect. Solution
The new 271-7442 Plug can not be installed on the older versions of the cylinder head. The new plug will not seal the oil rail on the older cylinder heads. If either of the plug assemblies should need to be replaced, ensure that the correct plug assembly is ordered. The plug determines whether the engine has the older head or the newer head. The older cylinder head has the 183-3902 Plug As that has a 3/4 inch socket head. The new cylinder head has the 271-7442 Plug which has a one inch hex head.
Illustration 1 g01411840
(1) 271-7442 Plug
Illustration 2 g01411848
(2) 183-3902 Plug As