In resent years, dynamic studies of valve mechanisms in the internal combustion engine have dealt with peculiar phenomena such as valve jump or bounce which occurs at high speed operation. These studies have contributed to the reduction of valve mechanism problems.However, one of the most severe problems is the wear of the valve face or seat. The dynamic study of valve mechanisms can be applied to this problem. It can be concluded that the impulse force working on the valve at the closing moment is the most effective factor to influence this problem. But, this impulse force has not been closely understood from the point of view of valve vibration mechanisms.This paper describes how the five mass model can simulate the valve mechanisms dynamically, and express the impulse force rather than the valve motion or pushrod force used previously. The results of the calculations agree very well with the experimental data and the new knowledge acquired indicates that the impulse force does not necessarily increase with rising cam speed.