Dynamical properties of 3C, 2H, 4H, 6H and 15R SiC polytypes have been calculated using a modification of Tersoff's potential for covalent multicomponent systems. Structures and vibrational frequencies are in good agreement with experimental results. For uniaxial polytypes, the dependence of the optical frequencies on propagation angle, has been studied. The relative intensity of Raman bands has been calculated using a bond polarizability model. Isotope shifts, phonon eigenvectors and relative phase for longitudinal and transversal modes of 3C SiC for the dispersion branches along the direction have been determined and compared with experimental results.