In the first part of this paper an overview of smooth and non-smooth multibody dynamics is given and numerical simulation tequniques for non-smooth multibody systems with impacts are considered. The second part deals with valve springs and different existing valve spring models. A new valve spring model, based on the approximation of the spring as a curved beam, is presented and validated using a test rig. The paper concludes with the integration of the new developed and implemented valve spring model in a complete valve train simulation. The application example allows to compare between the new valve spring model and a multi-mass model regarding to computational time using different integrators with smooth and non-smooth contact mechanics.