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Calculating the forces and displacements of valve linkages and springs is considered a problem of engineering vibrations. The periodic lift function of the cam is approximated by a Fourier polynom. For each harmonic of this polynom, the forced displacement amplitudes of the various masses of the vibration model system are determined with the methods customary in vibration practice. By adding up the individual harmonics of amplitudes it is possible to obtain for each mass of the system again a Fourier polynom approximating to the solution aimed at. This in turn enables the forces between the masses to be easily computed from the known motions of the masses. The advantage of this approach over the conventional procedure, where solution is attained by numeric integration of the equations of mass motions, is on the one hand a saving in time and hence lower computer cost. On the other hand, application of the procedure recommended here will enable the number of model masses to be significantly reduced by generalizing the model. To this effect, in lieu of valve springs, pushrod and valve stem, the mass points are connected by bars offering a continuous distribution of elasticity, mass and damping. The model thus obtained corresponds to reality to a greater extent than the current multi-mass model where individual masses are linked by springs and damping elements that in their turn have no masses. The present analysis also seeks an answer to the question as to how much the cam shape has a bearing upon the excitation of vibration. The computation method is substantiated by formulas and explained by examples.