In this work different contact models within valve train simulations are investigated. Two basic approaches are opposed, namely rigid and flexible models. The rigid model is described by a unilateral constraint, for the group of flexible models a linear spring-damper-element and different variants of H_ERTZIAN contacts are used. Frictional effects are considered by C_OULOMB's law in the original and a regularized formulation. The models are discussed in terms of their influence on the dynamics of the valve train system, especially when they are used in diverse configurations. For the numerical analysis the system size has been varied and extended to the entire valve train with all cylinders and valve mechanisms.