A method of constructing a spark plug that has positive and ground electrodes configured such a spark plug defined between the positive and ground electrode extenders comprises an elongate channel which opens axially and away from the body and is substantially unobstructed in the axial direction to provide better ignition resulting in improved fuel economy. The method involves taking a body part of a conventional spark plug and welding an adapter part to the body part to produce a spark plug with the elongate channel.