In the present paper, starting from a first attempt design of engine components, a CAD/CAE integrated approach for designing engine is proposed. As first step, some typological quantities are setting in order to define the designed engine, for example the number of cylinders, displacements, thermodynamic cycle and geometrical constraints. Using literature approach and tailored design methodologies, the developed software provides the geometric parameters of the main engine components: crankshaft, piston, wrist pin, connecting rod, bedplate, engine block, cylinder head, bearings, valvetrain. Form the geometrical parameters, the developed software, using 3D CAD parametric models, defines a first functional model of each component and of their mutual interactions. Then a numerical analysis can be evaluated and it provides important feedback result for design targets. In the paper the particular case of a crank mechanism model is presented. The assembly of crankshaft, pistons, wrist pins, connecting rods are modeled by means of a full parametric approach and driven by the first geometrical design. Then a numerical validation of the solution is done and a feedback procedure is taken into account. In that case, a structural modification on the crankshaft is used for a dynamic torsional requirement. The proposed software proves to be a useful and quick instrument for a conception of a new engine. As a consequence, it is an interesting method to reduce the design time and costs, allowing automatic optimization techniques.