"RUNNING IN."

Waipa Post, Volume 48, Issue 3470, 24 May 1934, Page 6

"RUNNING IN."

THE MODERN METHOD. New engines, like young children, can be just as badly harmed by oversolicitous care as by thoughtless handling. This (states "The Motor") is one of the most important deductions that can be made from the latest research results—researches which have materially altered ideas as to the best way of carrying out the run-ning-in process. The engine of a new car turns stiffly for two reasons; first, the bearings and pistons are fitted tightiy, with minimum clearances, and secondly, the working surfaces, however carefully machined, are actually marred by microscopic irregularities. In the course of running in these surfaces are burnished until smooth and, as a result, the clearances increase; both these changes tend toward a reduction of friction. Burnishing produces heat and yet, if the surfaces are to be smoothed with reasonable rapidity, a certain amount of pressure is essential. Consequently, the first and most important requirement is an adequate supply of lubricant that will reduce friction and carry away the heat generated. Not only must the ownerdriver maintain the proper level in the sump, but in addition it is essential that he should use a reasonably light oil of the right grade. Starting From Cold. Particular care is necessary when starting a still engine from cold, because the oil is still thick and slug-1 gish. lit has to flow from the pump through a filter, a number of tiny passages and a series of tight bear-, ings, before it is thrown into the cylinders by the rotating crankshaft; consequently very little oil reaches the bores and pistons during the first couple of minutes. This is where the over-cautious owner is apt to make his first mistake; he sets the engine at much too low an idling speed when allowing it to warm up. In so doing he extends, the time required and reduces the quantity of oil thrown into the bores. The proper speed is from 1000 to 1200 r.p.m., Avhich can be roughly judged from the fact that it is about the rate at which the engine revolves when pulling the car at 20 m.p.h. on top.

Too low a working temperature does an engine far more harm than running too hot. The products of combustion condense on the cold walls of the cylinders and set up a corrosive action which has been shown to be one of the most likely causes of undue wear. Thermostat devices are of great assistance in this connection Points to Watch. The golden rule for running-in a

new car on the road is to avoid sustained periods of hard work, which will raise the oil temperature to an unsafe figure. Provided that this is remembered, short bursts of speed, at intervals, will be found advantageous. Othei'wise, general running can be 38 m.p.h. o'n top and 21 m.p.h. on the third gear. On the other hand, while over-rev-ving is harmful, the engine should not be allowed to labour at full throttle; it is, therefore, better to change down on a stiff hill than to hang on to top gear, always provided that an excessive speed is not maintained. After 500 miles have been covered it must 'not be assumed that the engine has suddenly become transformed into a free-running unit. Care is still required, and the best method is to increase the load and speed bit by bit, with more frequent fullthrottle periods, so that by the time 1000 miles is reached the car is being quite freely used. Clean the Filters. At this stage it is very important to have the filters cleaned, the sump thoroughly drained, and to refill with fresh lubricant. The running-in process results in the abrasion of a certain amount of metallic dust which mixes with the oil and is harmful to the bearings. The whole process is undoubtedly assisted by using one of the many special running-in compounds now available, which contain colloidal graphite in the form of tiny particles in suspension. The graphite forms a greasy film on the metal surfaces, safeguarding them from seizure and helping them to attain a smooth, long-wearing "skin."