The engine's inevitable trend to higher output and speed has involved a lot of perplexing problems to be solved in valve gear design. Among all these problems, in modern engines, valve linkage separation has grown to be of particular interest, since the engine's great reliability at operation beyond the rated speed has come to be the first requirement. Thus valve ‘jump’ and valve ‘bounce’ are now not the valve linkage separation phenomena that might occur beyond the maximum engine speed, but those that should be expected within the speed ranges where the engines are driven with a considerable probability.This paper deals with the new simulation model, basically composed of a double mass system, which is conceived for sound reflection of such intricate valve train behaviors at the higher speed range of operation. Thorough validity of the proposed model has been confirmed by experimental investigation in which a minute observation of valve linkage separation as well as the behaviors of each component of the valve train was made. The new simulation will make it possible at the design stage to forecast the valve gear behaviors at high-speed operation, which in due course will make it easier to carry out the swift and reasonable design of the valve train for greater reliability and durability of the engines to be put into production.