STUDY ON VALVE RECESSION CAUSED BY NON-LEADED GASOLINE.

The amount of wear debris from the exhaust valve seat in condensed water of exhaust gas was continuously measured by means of the R. I. method. At the same time, rotational and lateral motion of the valve were measured. Then the mechanism of the exhaust valve recession in using lead free gasoline as a fuel of the automobile engine was made clear as follows: Cast iron flakes were removed from the valve seat and they adhered to the valve surface. And then, these deposits wore off the valve seat because of rotational and rolling motions of the valve. Especially, during about 20 minutes after the running conditions were changed, the valve motions became more violent and the wear also increased rapidly. Thus the overall abnormal wear of the valve seat was caused mainly by above mentioned transient phenomenon.