VALDYN is a dynamics simulation package which has been specifically
  developed for valvetrain and drive system analysis. The package
  incorporates a graphical user interface which allows complex models to be
  constructed rapidly and accurately. With its detailed "building block"
  models of valvetrain components, VALDYN can be significantly more
  efficient than many of the general purpose dynamics tools as model
  refinement is focussed on those aspects critical to valvetrain dynamics.