Patent ID: 7975665

Claim:
A spark plug, comprising: a center electrode; an insulator having therein an axial bore that extends in an axis direction of the center electrode and accommodating the center electrode in the axial bore; a metal shell surrounding and holding the insulator in a radial direction, said metal shell having a threaded portion for mounting the spark plug on a mounting portion of an internal combustion engine; a cylinder-shaped cylindrical portion extending from the threaded portion of the metal shell toward a front end portion of the center electrode; and a ground electrode having one end joined to a front end of the cylindrical portion and another end disposed opposite to a front end portion of the center electrode to form a spark discharge gap therewith, wherein the insulator projects beyond the front end side of the cylindrical portion, wherein the cylindrical portion includes one or more ventilating portion which communicate with an inside and an outside of the cylindrical portion, said ventilating portion comprised of a notch.