Engine with noise reducing exhaust valve arrangement
 An arrangement for reduction of exhaust noise in an internal combustion engine comprising in a preferred embodiment a two-cycle diesel engine having two or more exhaust valves per cylinder and separate cam lobes for actuating two groups of one or more valves. The lobes are arranged to stagger the openings of the two valves or groups of valves and to close all valves in a cylinder at the same time. The gas flow area past the earliest opening valve during the period before the second valve opens is controlled to restrict exhaust gas flow, thus limiting the exhaust blowdown pulse and exhaust noise from that source. Preferably, the initial flow restriction is provided by seating the early opening valve heads in countersunk seats with a predetermined radial clearance around the head which acts to restrict the flow in the initial opening period. 
General Motors Corporation
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F02F F02B F02B F01L
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Lawrence D. David E. Terrence S.
Peterson Bennett Trasatti