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Show KNOCK IS 101 AIMS BOOST On Automobile It May Mean Warning of Impending Trouble Some one onco said that every knock is a boost. II may be so on the car. If you will but understand that the knock la a warning of trouble; that it may mean dangor, or ultimate breaking down of the motor or car appliances, ap-pliances, and that when you get at the car and find out what the knock is and-remedy tho trouble you boost your chances of Betting home safely, and perhaps boost the chances of having an engine in the car worth mentioning. Now, there are some fifty-seven varieties va-rieties of knocks; how shaMl you know which variety you have? Some of them have troubled tho wise heads of the factories and the experts of the garage ga-rage and service station. But with care you may locate and eliminate the ordinary causes. Carbon Knock Frequent. Perhaps the most frequent knock is that which comes from carbon in tho cylinders. Of course there ought not to be carbon there, but faulty carburetion, faulty lubrication and faulty compression do produce it. Many engines, even on the high grade cars, have a proneness to accumulate carbon, partly due to the poor grades of gasoline of the present day. Most high-power engines are constructed to have as high compression as possible, almost to the point of pre-ignitlon; then when a film of carbon forms in the combustion chamber It raises the compression so that there is pre-igni-'tion aud a knock. We onco had" a car with this trouble from the time .we got it until the agent, after many trials, found a solution. This was to put a one-quarter Inch fiber fi-ber gasket under the cylinder, raising it and lessening the compression. Thero were, of rourse, other adjustments adjust-ments to make, such as the water connection, con-nection, valve push rods and things of that sort. But ft did the trick; tho i carbon knock was stopped and instead I of cleaning out carbon every 100 miles or so it ran 1!000 before it, was cleaned. Later a friend had a car with the same trouble and found relief -in the fiber gasket, which has the effect of increasing in-creasing the size of the combustion chamber, thus lessening the compression. compres-sion. Not All Carbon, However. une should not jump to the conclusion con-clusion that every knock comes from carbon, however. Knocks which proceed pro-ceed trom a loose connecting rod bearing, bear-ing, loose cylinder, lack of lubrication or a broken moving part might cause almost immediate damage to the motor, mo-tor, so it Is well to determine what is at fault. Shut down the engine until you know one of these things is not making the noise. A piston slap, tho noisy, or a clicking, oil pump, however, is noi going to break up the. machine. When you go to the expert and he cannot Immediately locate the cause of a knock he will call It a "gas knock" and say there is no remedy for it. Now, I do not know what a "gas knock" is. It is a term for the knock which is elusive, and some engine knocks come wilh tho motor the manufacturers man-ufacturers have not thought it necessary neces-sary to eliminate them, being harmless. harm-less. "Lean Mixture" Fallacy. We put on a new cam shaft gear on a school car to eliminate a knock and had a worse one. It look a long time to find that in forcing on tho gear the shaft had cracked the ,hub and rim, I making the alignment of two teeth' such that a knock was produced. Sticking exhaust valves, due to gummed gum-med oil, make an elusive knock, be-causo be-causo the stem does not spring back on the push rod properly and when the two meet there is a thump. Set it down that lean mixture or, over-advanced spark do not cause knocks, though it Is a common statement. state-ment. They do exaggerate and bring ' to our attention other faults, such 33! worn pistons of cylinders and other wears which becomo audible. Where to Look. Here is a list of things which have been found to produce knocks; discovery discov-ery of the cause naturally suggests the cure: From mechanical looseness, due to improper adjustment or wear; loose crank pin bearing of connecting rod; crank pin bearing out of round; main crank shaft bearings loose; bearings too tight; wrist pin loose in piston or in connecting rod; wrist pin out of line with crank shaft, causing side slap; ,' piston ring loose in slot or broken;! cam follower guide worn; cam loose on shaft; flat spot worn In cams; fly-1 wheel loose where keyed to crank shaft; fly-wheel out of balance; worn and broken timing gear teeth; cylinder cylin-der loose on base; timing gears loose on shaft; engine loose on frame; piston pis-ton too small, causing slap; poor pushrod adjustment gap too large; sticking valves; spark plug too long, touching valve; magneto coupling loose; fan belt coupling striking pulley; pul-ley; fan blades striking somewhere; worn cylinder; bent crank shaft. Faulty ignition Spark advanced too far; spark too late, causing overheating; overheat-ing; short circuits in ignition system, causing irregular spark; spark plug points defective and overheating; plug in poor location; wrong timing too late, too early, worn order; dirty distributor, dis-tributor, which diverts current. Faulty carburetion Pre-ignition, due to excess of carbon; rich mixture, causing overheating; lean mixture, causing worn parts to knock, no- |