What Your Camshaft Needs From Your Engine's Oil.

In engines that do not use a roller cam follower, it is the job of the oil to minimise destructive friction between the cam lobe and what ever cam follower the valve train uses.

This job is done in 3 phases.

Firstly the oil should maintain a film between the lobe and follower. Second it should encourage oil to stay between the lobe and follower after the film has broken down. Lastly it should provide a residual friction reducing barrier when no oil is left between the lobe and follower.

The ability of the oil to maintain a film between the two parts under increasing load is measured as Film Shear Strength. This is often confused with viscosity but in reality is a product of many factors including oil type, quality and additives used.

As the oil film starts to break down under increasing load, the ability to maintain an oil presence between the parts is measured as Hydrodynamic Lubricity. Different base oils will have a different amount of inherent hydrodynamic lubricity. Mineral base oils and ester based synthetic oils have better hydrodynamic lubricity than group 4 synthetic base oils. It is often improved with an additive such as ZDDP (Zinc Dialkyldithiophosphate).

The task of reducing friction when no oil is left between the parts is left to friction modifiers that have bonded to the surfaces. Molybdenum Disulphide (Moly) is one common additive used for this. Molybdenum Disulphide has an affinity for ferrous metals, and will bond to the surface of both the camshaft and lifters, remaining after the oil has been forced out. Friction modifiers provide a limited amount of protection against damaging wear when metal to metal contact occurs. The valve train design, including valve spring pressure, must be such that metal to metal contact only occurs for very short periods if the lobe and follower are to have a long and happy life.

Kennelly recommend using a Moly based paste, such as Rocol ASP, to lubricate the cam lobes during assemble, and running a ZDDP, or ZDDP and Moly, additive in your engine oil during the running in period...for the sake of your new cam.