MORE THAN SEVEN YEARS of investigation of the problem of preventing valve-seat erosion under severe operating conditions in motor-truck and motorcoach engines are reviewed briefly. Engineers are said now to be generally agreed that an insert of some non-ferrous material is the only means of obtaining a valve seat that will stand severe service.
A theory for the cause of a thin spotty deposit or pick-up on the valve seat that accelerates erosion is advanced, and this deposit is said to be absent on valve seats made of non-ferrous metals. Aluminum bronze gives satisfactory results but is difficult to secure to cast-iron cylinder-blocks because of its greater coefficient of expansion.
Several partially successful methods of securing aluminum-bronze rings to cast iron are shown. A method that is applicable to one alloy which has reduced erosion under the most severe operating condition to such an extent that it is almost negligible is described.