Running-In Methods

Northern Advocate, 12 June 1937, Page 2

Running-In Methods

CARE OF NEW ENGINE. Argument is proceeding in the English motoring journals regarding the correct methods of running-in a new or rebored engine. Many of the correspondents not only regard the timehonoured 20 m.p.h. system as obsolete, but as deleterious. >’

One factor that is obviously not realised by many people is that it is not speed alone that does harm, but speed plus load, or mere overloading regai'dless of speed. Far more harm will be done to an engine by sudden throttle opening or by slogging up a steep incline at, 15 m.p.h. with the throttle wide open than by cruising along at 45 m.p.h. with the throttle only a quarter open, especially during the first 1500 miles.

Speeds of 30-32 m.p.h., with frequent lifting of the foot from the accelerator pedal, are generally accepted as good practice in driving a new car on flat roads. The throttle closing has the effect not only of reversing temporarily the bearing loads so as to improve their oil distribution, but also allows the piston tops to cool, and draw tip oil to the top ring. Upper cylinder lubrication, and the use of colloidal graphite in the oil many consider should be 'stressed by the manufacturers as emphatically as the need for gentle methods in running-in.

Many manufacturers content themselves merely with advice against exceeding a certain top-gear maximum. A few give a table of maximum speeds for each gear, but very rarely is anything provided which is so comprehensive as this table:—

For the car for which this table was compiled, the lower speeds correspond to about 1000 r.p.m., and the higher to 2750 r.p.m., or approximately 66 per cent, of the revs, at peak h.p., and on that basis a similar table could be compiled for any car, the gear ratios and wheel sizes of which were known. Extremely low engine speeds are not advised because of the fact that cylinder lubrication is apt to suffer by reason of insufficient oil mist being thrown off by the crankshaft, as well as the heavy bearing loading which will be introduced by hard pulling at low speeds. Another point mentioned is the desirability of an oil change after the first 200 miles. The reason for this is that in this distance, . unless the; em gine has had considerable bench running or road testing at the factory, abrasive particles dislodged from castings may be considerable. With modern systems of oil filtration now usually provided, however, this precau 7 Iron is less urgent than it was a few yeara ago.

Not under. Not over. First gear .. — 10 Second gear . . 5 17 Third gear ..10 23 Top .. 12 30