OLD PLUGS

Rotorua Morning Post, Volume 3, Issue 725, 28 December 1933, Page 7

OLD PLUGS

Experiments have demo'nstrated that appreciable deterioration in the running of an engine may be caused by using an "odd" sparking plug, or more than one, in either a fourcylinder or six-cylinder engine. The tests showed eonclusively that to secure the best results in acceleration, speed, hill-climbing, and freedom ! from engine vibration it is necessary to use a full set of four or six plugs all of the same "reach" and preferably all of the same make and model. Sparking plugs of various make and models differ in regard to (1) the shape, thickness, and designs of the electrodes; (2) the length of their reach (i.e., the extent to which they project into or towards the combustion chamber), and (3) tbe number of "points" across which the spark is a£ liberty to jump, as well as in the material and design of the insulator and body. As regards the shape and thickness s of the electrodes and the number of sparking points, it was found that these factors of differences are relatively unimportant. But when the odd ones differ appreciably from the others in length of reach, there is unquestionable deterioration in en- , gine performance. The greater the ; difference in reach, the greater th£ j deterioration and more noticeable the j roughness in running. If one could be quite sure that an | odd plug had precisely the same j reach as the others of a different . make and model, no deterioration in , performance might be observable . with it in use. Nevertheless, it is I advisable to use one set of plugs, and j not a variety. ■ j