Using the alternating frequency/time domain technique and statistical analysis, an efficient analytical technique has been developed to compute the mean values and variances of the crank's angular speed and driving torque for a stochastically defined internal combustion (I.C) engine. The I.C. engine is represented by a slider-crank mechanism with a discontinuous force on the piston due to the time-varying gas pressure in the cylinder. The tolerances on link lengths and radial clearances and uncertainties in pin location are treated as random variables. The validity of analytical technique is established by comparison with results from Monte Carlo simulation. The results from parametric studies are also presented.