Bulletin: TB1045

Subject: Cummins Engine CPL Cautions

Engine: Cummins 855

Clevite Part Number: All

Explanation:  The Cummins 855 is an extremely popular and flexible design. It can provide a wide range of horsepower and torque ratings by replacing performance parts such as turbocharger, pistons, camshaft, after cooler, fuel system components, etc. These components are listed in the Control Parts List (CPL).

Many of these CPL's are certified by agencies such as the EPA, CARB and various foreign authorities. These certified engines, in many instances, list a model year that the CPL met air quality standards.

An engine should not be rebuilt to a CPL of an earlier engine unless its certification matches the vehicle model year. To do so may be a violation of air quality standards.

An example of this is rebuilding CPL 838 or 840 to CPL 625, 676, or any other fixed time NTC400.

Service Engineering has received several inquires regarding horsepower upgrades on the 838 and 840 CP's. The customer usually indicates the engine operates very poorly, with a common symptom of excessive smoke. This is due to the fact that earlier CPL's 625, 676, etc. used a different rocker arm ratio. When the 838 and 840 CPL's are upgraded (to 400HP) with an earlier CPL the rocker arms are incorrect. While a complete set of rocker arms may be substituted this will still be a violation of air quality standards based on the correct model year.

Cummins used the STC (Step timing control) system for engines above 350HP and has never released a fixed time injector for the 88NT used in automotive applications.

MAHLE Clevite can assume no responibility for any engine components used in improper or illegal applications.