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Valve trains are highly burdened powertrain subsystem which has to undergo high fatigue cycles during its service lifespan. Wear enhances valve lash thus depreciating the performance drastically. Analytical advances have helped engineers to predict parameters such as wear, contact stresses, lubrication etc. to uphold the durability of valve train components. Most of the genset and industrial engines running at medium speed use type 5 valve train. In this paper, our study involves about crack induced “wear” due to Hertzian stress on rocker toe and the process followed to resolve the problem for a medium speed diesel engine We experienced the problem of rocker toe crack resulting in toe wear in field and on test bed. Our investigations led us to evaluate the life of a rocker toe by specifically developing a test cycle to reproduce the wear due to induced cracks as well as to assess the durability.

Parameters like brake mean effective pressure, mean velocity of the piston, hardness of the wear surface, oil film thickness, and surface areas of critical wear parts are similar for all the diesel engines. The mean piston velocity at the rated speed is nearly the same for all the diesel engines. The mechanical efficiency normalized to an arbitrary brake mean effective pressure (bmep) is dependent on the size of the engine. The engine life seems to be proportional directly to the square of a characteristic dimension namely, cylinder bore of the engine and inversely to speed and load factor for engines varying widely in sizes and ratings.