The disclosure relates to an improved flapper type saftey valve and valve housing for use in subterranean wells wherein the flapper valve is actuated from a horizontal closed position to a vertical open position by contact with a downwardly moving actuating sleeve. The top surface of the valve is elevated so that the bottom edge of the actuating sleeve always contacts the flapper valve at a position spaced from the axis of the pivot mounting, thereby assuring that the opening force applied to the flapper valve has a maximum moment arm in order to overcome any fluid pressure differential existing across the flapper valve. The valve is mounted in an eccentic bore on an eccentric mounting base and fully opened flapper valve provides maximum flow area through the valve.