Practical Hand Book of Gas, Oil and Steam Engines / Stationary, Marine, Traction; Gas Burners, Oil Burners, Etc.; Farm, Traction, Automobile, Locomotive; A simple, practical and comprehensive book on the construction, operation and repair of all kinds of engines. Dealing with the various parts in detail and the various types of engines and also the use of different kinds of fuel.

by John B. Rathbun

(141) Valves and Compression Leaks—Misfiring.

Owing to the intense heat in the cylinder, and the action of the gases on the valves the seating surfaces become ROUGH and PITTED which causes leakage and loss of compression. Exhaust valves cause the most trouble in this respect as they are surrounded by the hot gases during the exhaust stroke and are much hotter than the inlet valves.

To determine the value of the compression, turn the engine over slowly by hand.

Leaking inlet valves usually are productive of BACK FIRING or EXPLOSIONS IN THE CARBURETOR intake passages, or in the mixing valves, as flame from the cylinder leaks through the valve and fires the fresh gas in the intake.

MISFIRING OR LOUD EXPLOSIONS at the end of the EXHAUST PIPE are indicative of leaky exhaust valves, if the mixture is correct and the ignition system above suspicion. Misfiring caused by leaky exhaust valves is due to combustible mixture escaping from the cylinder to the exhaust pipe and being ignited by the succeeding exhaust of the engine.

If the engine has more than one cylinder, test one cylinder at a time, opening the relief valves on the other cylinders. Now take a wrench and ROTATE the inlet valve on its seat, for it may be that some particles of carbon or dirt have been deposited on surface of the valve seat which prevents the valve from closing properly. Rotating the valve will usually dislodge the deposit.

Try the compression again; if there is no improvement, rotate the exhaust valve on its seat in the same manner, and repeat the test for compression. ROTATING THE VALVES IN THIS MANNER WILL OFTEN MAKE THE REMOVAL OF THE VALVES UNNECESSARY. When the valves are closed the end of the valve stem should NOT be in contact with the PUSH ROD, or cam lever. Suitable CLEARANCE should be allowed between the end of the valve stem and the operating mechanism when the valve is closed; this clearance varies from the thickness of a visiting card on small engines to ⅛ of an inch on the large. If the valve stem is continually in contact with the push rod it cannot seat properly and consequently will leak. Wear on the valve seats and regrinding reduces this clearance, wear on the ends of valve stems and push rods from continuous thumping increases it. Keep the clearance constant and equal to that when the engine was new. On many engines this clearance is adjustable to allow for wear by lock nuts on the ends of the valve stems or push rods.

If the above attempts have proved unsuccessful remove the exhaust valve from the cylinder, if the valve is in a cage, remove the entire cage; this may easily be done on most types of engines. Always remove the exhaust valve first as the inlet valve rarely requires attention. With small engines, and engines having the valves mounted directly in the cylinder head it will be necessary to remove the cylinder head to gain access to the valves. In such a case use care when opening the packed joint between the cylinder and head, to avoid damaging the gasket.

The exhaust valves should be lubricated with Gas Engine Cylinder Oil, never with common machine oil on account of gumming and sticking, or with gas engine cylinder oil thickened with FLAKE GRAPHITE. Powdered graphite may be used with success without the addition of oil, but oil makes the application of the graphite much easier.

A cracked valve seat, due to expansion strains or to the hammering of the valve, is a common cause of compression leakage, and is rather difficult to locate as the leakage only occurs under comparatively high pressure. Leakage may also occur between the valve cage and the cylinder casting unless pains are taken to thoroughly clean the cage and the bore before fastening into place.

Warped valves are caused by overheating, the head of pallet of the valve becoming out of square with the stem, or by twisting on the valve seat. If warped valves are suspected the high point of the seat may be determined by means of the following test and should be carefully filed down until it is close to a bearing after which it may be ground down as described under pitted valves.

If the stems are now in good condition examine the seating surfaces of the valve pallets and cage or rings.

The seats should be bright and free from pits, depressions, or streaky blue discolorations. If the seats are deeply grooved from long continued leaks it is best to discard them and replace with new.

Pitted valves, and those slightly grooved or streaked should be reground by the use of a little emery flour and tripoli which operation is performed as follows:

Lift the valve from its seat and apply lubricating oil to the seating surface, then sprinkle a little flour or emery on the oiled surface and drop the valve back on the seat. Do not use coarse emery nor too much of the abrasive, a pinch is enough and will grind as rapidly as a pound. Take care to drop the emery only where required, do not sprinkle it over the engine or working parts as it will cause cutting and the destruction of the bearings.

Now turn the valve around in one direction for about a half dozen turns and then in the other direction for the same length of time, alternately, at the same time applying a moderate pressure on the valve. Small valves may be rotated with a large screw driver entered in the slot found on the valve plate, but the handiest method is with a carpenter’s brace in which is inserted a screw-driver bit.

Never turn the valve around and around in one direction continuously as this movement is liable to cause grooving, alternate the direction of rotation frequently with occasional back and forth movements made in a semi-circle.

Do not press heavily on the valve, use only enough pressure to insure contact between the two seating surfaces.

The valve should be lifted occasionally from the seat to prevent grooving, and to redistribute the abrasive, and then dropped back, after which the grinding should proceed as before. Remove the valve after it turns without friction, wipe it clean, apply fresh oil and emery and grind once more. When the grinding has removed all pits and ridges, and presents a smooth even surface, the grinding is complete. To test for accuracy of grinding place a little Prussian Blue on the seat, if the valve is ground to a perfect surface the blue will show uniformly spread over the seat, if the grinding is incomplete bare places showing high spots will be seen. It is a good plan to finish the grinding by using a little Tripoli with oil after the emery has removed the pits and high spots, as Tripoli is finer than emery and will smooth down scratches made by the emery.

After the grinding has been performed to your satisfaction, wash the valve, valve stem, and guides thoroughly with gasoline and kerosene to remove the smaller traces of emery, to prevent wear and cutting.

When the valves are ground in place on the engine stuff up all openings or parts of the cylinder to prevent the emery from gaining access to the bore. After grinding is complete wipe off surfaces thoroughly and remove waste used for stuffing.

CHAPTER XIII
TRACTORS AND FARM POWER

Because of our increased population, which results in a greater planted acreage, and the scarcity and increased cost of farm labor, farming has rapidly developed into an industrial science. Where formerly the farmer was content to perform certain parts of his work by hand, he today employs machinery for the same task, and is far more particular as to the working of his soil and the cost of production per acre. By the use of machinery his crop is marketed at less expense, in a shorter time, and he has more time in which to enjoy life than ever before.

The modern gasoline and oil engine has been the greatest factor contributing to the farmer’s ease and prosperity for it has eliminated the terrors and drudgery of plowing, churning, watering stock, sawing wood, threshing, and has besides given him many of the conveniences of city life, such as running water and electric light. The benefits of power are not only conferred on the farmer but his wife as well for the small domestic engines have saved the back of the house wife during the strenuous period of harvest time.

One of the difficulties of farming is the necessity of doing certain work in a limited time or else suffering a heavy loss. The breaking, the plowing, the harvesting, and the threshing each must be done at a certain time, often within a few days of each other in order to obtain the benefits of the best weather conditions. Threshing starts as soon as the grain is ready, and if rain interferes with the threshing, the farmer can start plowing immediately if provided with a tractor and thereby gain the undoubted benefits of fall plowing. Plowing at harvest time has much to do with eliminating weed seeds for the weeds are turned under while green, the seeds sprout and commence their growth and are winter killed before they reach maturity. In this way the field is practically freed from weeds in the spring. When the weather again becomes suitable, the threshing may be resumed and when completed he can again turn to his plowing.

Operator’s View of the “Big Four” Tractor, Showing the Four Cylinder Engine in Place.

Gas power is not to be considered merely as a substitute for animal power for the engine not only performs the work of the horses but also performs work that no horse can do, and does it with far less expense. In the hottest weather when horses are dropping in the broiling sun, the tractor moves tirelessly through the fields. Every farmer knows the expense attached to keeping a horse in the idle winter period for it must be fed, watered, and cared for, work or no work. When the engine is idle it costs nothing except for the interest on the investment, while animals grow old and are subject to disease whether they work or not.

The time of plowing and harvest is short and requires quick work, and continuous work. Horses cannot be driven at plow faster than one mile per hour, and cannot be worked more than 10 hours per day, while the tractor under suitable conditions can travel 2 to 3 miles per hour, and keep at it twenty-four hours per day. An ordinary tractor can break from 20 to 40 acres of ordinary loam per day and will plow in cultivated land from 40 to 50 acres per day.

The same factors govern the fuel consumption of a tractor that govern the rate of plowing, that is, the character of the soil and the depth of plowing. On an average, 1½ to 2½ gallons of gasoline will be used in breaking an acre of sod, and 1 to 1½ gallons of gasoline in plowing stubble. As kerosene contains about 18 per cent more heat per gallon than gasoline, the quantity of fuel used by an oil tractor is correspondingly less. When used for pulling wagons on the road at about 3 miles per hour the fuel consumption will approximate 4 gallons per hour, this consumption varying of course with grades, etc.

Thirty horse-power, at the speed given above represents a draw bar pull of about 9,000 pounds, which is equivalent to the tractive effort of from 30 to 40 horses, were it possible to concentrate the pull of so many horses at a single point, at one time. It would of course be impossible for the horses to maintain this effort for as long a time as the tractor. On a level road it will take about 100 pounds tractive effort for each 2,000 pounds of weight in the form of road wagons (including the weight of the wagon). The number of wagons that can be drawn with a given draw bar pull can be easily figured. When pulling on a grade, the effective draw bar pull will be reduced in proportion to the extent of the grade. While no fixed rule can be given regarding the number of plows that can be handled by a tractor, the average machine can pull six to eight breaking plows and from eight to twelve stubble plows, depending on the character of the soil and the depth of plowing. When the conditions permit the use of a greater number of plows, than specified above the amount of work done will of course be greater.

A tractor can haul four ten foot seeders and two twenty foot harrows and cover 7 or 8 acres per hour at a cost of from 12 to 15 cents per acre. At harvest time the tractor will also effect a great saving in time and expense for the average machine will handle five or six eight foot binders, making a cut of nearly 50 feet wide, and this can be kept up for 24 hours at a stretch.

A tractor of the average output can handle any separator, and with a 44″ cylinder machine can turn out from 2,000 to 3,000 bushels of wheat and 5,000 bushels of oats in a ten hour run. It will also handle any of the largest shredders. For irrigation work, silo filling, and wood cutting it is equally efficient.