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THE acute operational problem of spark-plug fouling in both the aviation and automobile industries is discussed in this paper, with special reference to the use of a tricresyl phosphate scavenger mix, which has been found to permit the laboratory aviation engine to run for 62 hr without fouling. The mechanism by which tcp relieves spark-plug fouling is believed to be the prevention of formation of metallic lead, but additional factors include the formation of lead salts having low electrical conductivity; the reduction in deposition of free carbon, and the production of soft, powdery deposits, which slough off easily, compared with the usual hard, glazed form. The successful use of tcp, as indicated in both laboratory and field tests, points to a future in which spark-plug fouling may become one of the minor causes of ignition failure.

SEVEN HUNDRED tons of iron, estimated by the authors to be worn annually from the cylinder bores of American automotive engines, cause an annual engine repair bill believed to exceed $1,000,000,000. A large part of this wear is due to corrosion, particularly in severe service such as gasoline-powered delivery vehicles or stationary diesel installations. Test results indicate that wear rates can be materially reduced by the use of crankcase lubricating oils containing high concentrations of alkalinity. The authors also present examples of radiochemistry research. Radiotracers are used to prove that oil consumed by the engine carries with it the iron debris which it contained at the moment of consumption.

A NEW technique is described utilizing a dynamic micrometer to observe valve motion during actual operation under simulated highway conditions. Using this instrumentation, studies were conducted on the effect on valve life due to dynamic sticking resulting from additive concentration, valve motion, and valve flexure. The test data indicate that exhaust-valve burning in passenger-car engines appears to be due principally to valve-face corrosion.