The original equipment manufacturer (OEM) Cummins camshaft is constructed from chill-cast ductile iron. This manufacturing process imparts a very hard surface to the camshaft, crucial for longevity in the demanding operating conditions of an engine. While the exterior is exceptionally hard, the core possesses a degree of softness. This design allows the camshaft to effectively manage torsional forces in a wide range of applications without fracturing. However, limitations become apparent when a camshaft engineered for approximately 200 horsepower and 2,800 rpm is pushed beyond 5,000 rpm. Furthermore, the challenges are compounded with the use of large injection pumps, heavy valve springs, and high-lift camshaft profiles.
High-lift camshafts, coupled with heavy-duty valve springs and large capacity injection pumps, generate cyclical torsional forces that significantly exceed the design parameters of the stock camshaft. Frequently, camshaft failure occurs between the nose and cylinder number 2, or between the nose and a journal where the hydrodynamic oil film has been compromised. Upgrading to a steel camshaft largely mitigates breakage caused by torsional harmonics. However, steel camshafts remain susceptible to failure due to journal seizure. Cummins B, ISB, and ISBE engines, contingent on the Control Parts List (CPL), are equipped with either one or two bearings for the seven journals. The remaining five or six journals operate directly within the engine block. When high-lift camshafts and substantial valve spring pressure are employed, the camshaft can overcome the oil film separating it from the block, leading to seizure. To prevent this, line-boring the block and installing journal bushings is a recommended modification.
Modifications to the engine block to accommodate camshaft journal bearings become beneficial when using a camshaft with specifications exceeding 210 degrees of duration at .050″ lift, a lobe lift greater than .340″, nose pressure exceeding 420 lbs, or when approaching engine speeds of 5,000 rpm.
A steel camshaft becomes a highly advisable upgrade if your engine operation is consistently near or beyond 5,000 rpm, or if you are utilizing a 13mm P-pump injection system, indicating a high-performance build where Camshaft Performance is critical.
Example image insertion points and ALT texts (assuming images from the original context would be available to illustrate these points):
...Ductile iron. This manufacturing process imparts a very hard surface to the camshaft, crucial for longevity in the demanding operating conditions of an engine.
While the exterior is exceptionally hard, the core possesses a degree of softness......journal where the hydrodynamic oil film has been compromised. Upgrading to a steel camshaft largely mitigates breakage caused by torsional harmonics.
However, steel camshafts remain susceptible to failure due to journal seizure...
...block, leading to seizure. To prevent this, line-boring the block and installing journal bushings is a recommended modification.
Modifications to the engine block to accommodate camshaft journal bearings become beneficial when using a camshaft with specifications exceeding 210 degrees of duration at .050″ lift...
