Explain Quench to me.....GO!

Actually - there is. It's the entire perimeter of the piston. The dish in the center is the floor of the combustion chamber and they seal off the outboard areas away from the spark plug. Two valve engines are not competitive with 4 valve when sized and equipped similarly. The 2-valves are just too handicapped in terms of ability to move air. They are just a lot chaper to manufacture.