Some one at the tech hot line said they see about 7 stuck valves a month because of brand new trucks sitting for months on dealer lots(with out starting the motors), valve stems rusting up. A week ago I did one and they said if the piston just had smiley faces, just do the head and gasket(and push rod) . No marks on the head but it looked like rough acne on the piston & head of that cylinder with the valve still open.