Experiments were conducted with the Ford V-8, 5.0L (302 C.I.D.) engine to investigate the effects of exhaust system design on engine performance. Five header manifolds were designed and tested both on an engine dynamometer and in a vehicle. The results are compared with the production exhaust systems and with predicted results based on exhaust tuning theories. Dynamometer engine tests were also conducted to determine the effect of the muffler and catalytic converter location on exhaust tuning. In addition, backpressure sensitivity studies were made and these data are compared with the results obtained through exhaust backpressure — power loss tests on competitive domestic vehicles.