The criteria used at present for evaluating valves [i, 2] (coefficient of clear opening, coefficient of drainage, specific leakage, and dead space of valves and valve seats) do not evaluate the design features of air distributors and their effect on the technicoeconomic operational indexes of piston compressors, Thus, a large clear opening of the valve (passage section) usually 4ncreases gas leakages through the seal edges and enhances the dead space. Valves with extremely poor spring pressure have high drainage coefficient which ultimately delays the seal operation with adverse consequences.