Oxy-acetylene welding manual

by Lorn Campbell

Fig. 86.—Removing Carbon from U. S. Army Truck, by the Oxygen Process, at the Ordnance Welding School.

Fig. 87.—Carbon Burning Apparatus. The Small Copper Tube A is Flexible and can be Bent in any Shape Desired.

(156) To remove carbon from a gasoline engine, first shut off the gasoline in the line and allow the engine to run until all gas has been removed from the carburetor. This is merely a safety measure. If a vacuum feed is used, the vacuum tank is drained, as it would require much time for the engine to consume this amount of gas. The hood of the car is then removed and all parts of the motor on the side where the burning is to be done are covered with asbestos paper or by a heavy piece of canvas which has previously been dampened. This is to keep the sparks from dropping into the apron or oily parts of the machine. Remove the spark plugs and see from the condition of these spark plugs whether the cylinder is dry or oily. An oily cylinder will burn out much more rapidly than when dry. This can be detected very easily from the condition of the spark plugs. It is recommended that only the spark plugs be removed as the removal of the bonnet or any larger portion will require much more oxygen and will not produce as satisfactory results as when the oxygen is introduced through a small opening.

(157) Place the carbon removing apparatus, which consists of the oxygen drum, regulator, a length of hose and carbon burning torch, the latter being made up principally of a shut-off valve and a long length of small copper tubing as shown at A in [Fig. 87]. Turn on not over twenty-five pounds oxygen pressure as far as the torch, and the apparatus is then ready to use. With the torch inserted through the spark plug hole in number one cylinder, that is, the one nearest the radiator, guide the rise of the piston until it is at the top of the stroke. This means that both intake and exhaust valves are closed. On automobiles where a self starter is used, it will be necessary to use a crank for turning over the motor. With the piston at the top of the stroke and both valves closed, there is only a small portion of the cylinder head to be worked upon and this is the part which has the carbon deposit upon it. All machined surfaces and valve seats are fully protected and will not be subjected to any exposure during the burning. If the cylinder seems very dry, a teaspoon of alcohol or kerosene may be sprayed into it through the spark plug port, to facilitate the clearing of the carbon. If the cylinder is somewhat oily, this is not necessary. A match or burning taper is then held over the hole and a stream of oxygen will carry the flame down into the cylinder and ignite the carbon. As soon as this occurs, a small cracking noise can be heard and the carbon will run around the inside of the cylinder in a heated condition. The part around the valves should be cleaned off first, before going to the inner chamber, as this process does not seem to work very well if performed the other way. A roaring noise will be in evidence and the popping of the carbon from the surface as it frees itself may frighten the operator when attempting his first job, but there is absolutely no danger.

(158) It must be remembered that oxygen itself does not burn, but merely assists the other inflammable material in burning, therefore it is only the carbon which is contained in the cylinder that in this case does the burning. As soon as this is all consumed, there will be nothing else to burn and the sparks will die of their own accord. When this occurs, the operator will shut off his torch, blow the cylinder out with compressed air and replace the spark plug and then proceed with the next cylinder, which he will treat in the same manner. He must be sure, however, that the piston in cylinder number two, or whatever cylinder he is working on, is moved to the top of its stroke and that both valves in that particular cylinder are closed before he starts his burning. After all cylinders have been treated like number one and the spark plugs are in position, the gasoline is turned on (if the vacuum tank has been drained, it is best to fill this), and the motor started, with the exhaust “cut off” open, in order that any loose particles of carbon may be blown out.

(159) While this process is in very common use, and seems to be very simple, there are many who go through the steps without obtaining satisfactory results. It is considered best, if possible, in attempting carbon burning for the first time, to try it on some motor which is about to be overhauled, in order that the results may be studied so that the operator will not go blindly on, without showing some improvement. Many times only the high points are burned out, which will free the motor temporarily of some of its knocks, but within a week or so they will become evident again. He who will become proficient in learning carbon burning should apply himself and study his results.

(160) There are those who consider carbon burning injurious to the motor on account of the high temperature flame which they think is introduced. But it is ignorance as to the working principle of this process that makes them think this. When it is considered that a gasoline motor depends upon a rapid succession of internal explosions for its power, the folly of condemning a process of this nature, where absolutely no actual flame is used, will be seen. It is only the incandescent particles of carbon flying about that give any heat at all. After a cylinder has been burned or decarbonized, the hand can be placed upon it immediately, without any fear of being burned. Those motors equipped with aluminum pistons may be handled in the same way as those of cast iron, and when properly used this method of decarbonization is very satisfactory.

(161) Many times it is asked how often carbon burning is to be recommended. This will all depend upon the type of motor, its condition, and to some extent, upon the lubricating oil and gasoline used, as well as the mileage of the car. If a machine is being run continually, it may be necessary to have the carbon removed about every two months, but conditions will tend to lengthen or shorten this time as the case may be. When the knocks are in evidence, and the loss of power is noticed, it is time for the carbon to be removed, and whether this is one month or two it is an error to continue running the car which is filled with carbon. Invariably the carbon burner is asked by his customer whether carbon burning will regrind valves; this and many other questions can be intelligently answered and explained to the questioner’s satisfaction if a careful study of the process is made.