Usage:
D346, D348, D349 Engines
Description of Change: A longer adjusting screw and a jamnut are available for parts service of the former adjusting screw in the rocker arms on the above engines. The longer adjusting screw permits use of a 12 point jamnut next to the rocker arm to keep the screw tight in the rocker arm. This prevents upward movement of the adjusting screw.
Formerly, the spring-loaded plunger with no jamnut, could allow relative upward motion between the screw and rocker arm. This causes thread wear on the screw and in the rocker arm. The longer screw and jamnut were never used as original parts in these engines because these engines were discontinued before availability of the new parts.
The two types of rocker arm assemblies furnished for parts service will also include the new screw and jamnut when the former arm assemblies are out of stock. See chart.
Adaptable To: The new parts are directly adaptable to all D346, D348 and D349 Engines.
Tighten the jamnut against the rocker arm to 42 ± 7 N·m (32 ± 5 lb ft). Write this new specification in the Specification Modules of the Service Manuals.
If desired, the new parts can be used to replace the former screw in new arm assemblies received for parts service.