These pushrod engines require a certain amount of
oil to be splashed onto the camshaft to lubricate the lifter /cam surface.This is also controlled by the rod side clearances, which ifbto tight will speedbup cam and lifter deteriotion if you idle for too long. Remember when a motor is started new for the first time it is taken directly to about 2500 rpm and kept there so the the cam and lifters can run in without grinding away.......