The optimal design of the valve train in a high-specific-power diesel engine was carried out.The original valve train is designed far from the material margins.The optimization objectives were the fullness coefficient and the time area

and the optimization method was the piecewise function method.By applying the restrictive conditions on each cam section

and the function was obtained.The dynamic and intake port performances of the original and the optimal valve trains were compared with each other.The comparison shows that the performance of the optimal valve train has been remarkably improved.