The automobile owner's guide

Q. What is the principle of the gasoline driven engine?

A. Gasoline when mixed with air and compressed is highly explosive. An explosion is a violent expansion caused by instantaneous combustion of confined gases. In the gasoline engine the mixture is drawn into the cylinder, where it is compressed by an advancing piston and then exploded by an electric spark, which sends the piston violently downward, and through the connecting rod imparts a rotary motion to the crank shaft. (See cut No. 147.)

Q. What are functions of the pistons?

A. On the downward stroke the suction of the piston draws the fresh gas from the carburetor, through the inlet pipe and valve, into the cylinder. The upward movement of the piston compresses the gas into a very small space, between the top of the piston and the depression in the cylinder head, known as the “combustion chamber.” (The compressed gases inert a pressure of approximately 60 pounds to the square inch.) At this point the electric spark, generated by the magneto, explodes the gas-driving piston downward, thus producing the power which turns the crank shaft. On the next stroke upward the piston drives the exploded gas out through the exhaust valve and pipe to the muffler. The accompanying cut shows clearly the relative positions of the pistons and valves during the different strokes.

Q. How is the connecting rod removed?

A. It is a vanadium steel rod connecting piston and crank shaft. Should the babbitt bearing become worn, or burned out through lack of oil, a knocking in the engine will result, in which case the entire connecting rod should be replaced. To make this replacement, (1) drain oil from crank case; (2) take off cylinder head; (3) remove detachable plate on bottom of crank case; (4) disconnect connecting rod from crank shaft; (5) take piston and rod out through top of cylinder.

Q. What is the valve arrangement?

A. One intake and one exhaust valve are located in each cylinder. The former admits the fresh gas drawn from the carburetor through the inlet pipe, the latter permits the exploded gas to be driven out through the exhaust pipe. The valves are alternately opened and closed (see Fig. 148) by the cams on the cam shaft striking against push rods which in turn lift the valves from their seats.

Q. What about valve timing?

A. In timing the engine the points of opening and closing of the valves are, of course, what should be considered. As the valves are properly timed at the factory when the engine is built, the necessity for retiming would occur only when such parts as the cam shaft, time gears, or valves were removed in overhauling the engine. In fitting the large time gear to the cam shaft it is important to see that the first cam points in a direction opposite to the zero mark (see Fig. 148). The time gears must also mesh so that the tooth marked (0) on the small time gear will come between the two teeth on the large gear at the zero point. The time gears now being properly set, the exhaust valve on No. 1 cylinder is open and the intake valve closed, the other valves being in the position indicated in cut No. 148. The opening and closing of the valves are as follows: The exhaust valve opens when the piston reaches ⁵⁄₁₆″ of bottom center, the distance from the top of the piston head to the top of the cylinder casting measuring 3³⁄₈″. The exhaust valve will close on top center, the piston being ⁵⁄₁₆″ above the cylinder casting. The intake valve opens ¹⁄₁₆″ after the top center and closes ⁹⁄₁₆″ after bottom center, the distance from the top of the piston to the top of the cylinder casting measuring 3¹⁄₈″ The clearance between the push rod and the valve stem should never be greater than ¹⁄₃₂″ nor less than ¹⁄₆₄″. The correct clearance is naturally halfway between these two measurements. The gap should be measured when the push rod is on the heel of the cam.

Q. What about the care of the valves?

A. They seldom get out of order, but they do get dirty as a result of carbon collecting on the valve seats. These carbon deposits, by preventing proper closing of the valves, permit the gases under compression to escape, resulting in loss of power and uneven running of the motor. If, when turning the engine over slowly, there is lack of resistance in one or more cylinders, it is probable that the valves need regrinding. As the “life” of the engine depends largely upon the proper seating of the valves, it is necessary that they be ground occasionally.

Q. How are valves removed for grinding?

A. (1) Draining radiator; (2) remove cylinder head; (3) remove the two valve covers on the right side of the engine; (4) raise the valve spring with lifting tool and pull out the little pin under the valve seat. The valve may then be lifted out by the head, preparatory to grinding.

Q. How are valves ground?

A. For this work use a good grinding paste of ground glass and oil procurable from auto supply houses. A convenient way is to put a small amount in a suitable dish, adding a spoonful or two of kerosene and a few drops of lubricating oil to make a thin paste. Place the mixture sparingly on the bevel face of the valve. Put the valve in position on the valve seat, and rotate it back and forth (about a quarter turn) a few times with a Ford grinding tool. Then lift slightly from the seat, change the position and continue the rotation, and keep on repeating this operation until the bearing surface is bright and smooth. The valve should not be turned through a complete rotation, as this is apt to cause scratches running around the entire circumference of the valve and seat. When the grinding is completed the valve should be removed from the cylinder, thoroughly washed with kerosene, and the valve seat wiped out thoroughly. Extreme care should be taken that no abrasive substance gets into the cylinders or valve guides. This can be avoided if the grinding paste is applied sparingly on the bevel face of the valve. If the valve seat is worn badly or smeared, it is best to have it reseated with a valve seating tool. This operation requires considerable skill, and perhaps had better be done by an expert mechanic. Care should be exercised against making too deep a cut, necessitating the retiming of the valve.

Q. What should be done when the valves and push rods are worn?

A. When the valves and push rods become worn so as to leave too much play between them, thus reducing the lift of the valves and diminishing the power of the motor, it is best to replace the push rods with new ones. The clearance between the push rod and the valve stem should never be greater than ¹⁄₃₂″ nor less than ¹⁄₆₄″. If the clearance is greater, the valve will open late and close early, resulting in uneven running of the motor. If the clearance is less than ¹⁄₆₄″ there is danger of the valve remaining partially open all the time. If replacing the push rod does not give the proper clearance, the valve should also be replaced. We do not recommend drawing out the valve stem, as the operation required, and the price of a new part does not warrant the time and expense necessary to properly do the work.

Q. What about valve springs?

A. When the valves fail to seat themselves properly, there is a possibility that the springs may be weak or broken. A weak inlet spring would probably not affect the running of the engine, but weakness in the exhaust valve spring causes a very uneven action, which is difficult to locate. The symptoms are a lag in the engine due to the exhaust valve not closing instantaneously, and as a result a certain per cent. of the charge under compression escapes, greatly diminishing the force of the explosion. Weakness in a valve spring can usually be detected by the following method: Remove the plate which encloses them at the side of the cylinder and insert a screw driver between the coils of the spring while the engine is running. If the extra tension thus produced causes the engine to pick up speed, the spring is obviously weak and should be replaced by a new one.

Q. What causes “knocking” in the engine?

A. There are several causes which may be enumerated as follows: (1) carbon knock, which is by far the most common, resulting from carbonizing of cylinders; (2) knock caused by a too advanced spark; (3) connecting rod knock; (4) crank shaft main bearing knock; (5) knock due to loose fitting piston or broken ring; (6) knock caused by piston striking the cylinder head gasket. When the engine knocks from any cause whatsoever, the matter should be promptly investigated by an experienced mechanic and the difficulty corrected.

Q. How may the different knocks be distinguished?

A. (1) The carbon knock is a clear hollow sound most noticeable in climbing sharp grades, particularly when the engine is heated. It is also indicated by a sharp rap immediately on advancing the throttle. (2) Too advanced spark will be indicated by a dull knock in the motor. (3) The connecting rod knock sound is like the distant tapping of steel with a small hammer, and is readily distinguished when the car is allowed to run idly down grade or upon speeding the car to twenty-five miles an hour, then suddenly closing the throttle, the tapping will be very distinct. (4) The crank shaft main bearing knock can be distinguished as a dull thud when the car is going up hill. (5) The loose piston knock is heard only upon suddenly opening the throttle, when the sound produced might be likened to a rattle. The remedies for these knocks are treated under their proper divisions.

Q. How is carbon removed from the combustion chamber?

A. First, drain the water off by opening the pet cock at the bottom of the radiator; then disconnect the wires at the top of the motor and also the radiator connection attached to the radiator. Remove the 15 cap screws which hold the cylinder head in place. Take off the cylinder head and, with a putty knife or screw driver, scrape from the cylinder and piston heads the carbonized matter, being careful to prevent the specks of carbon from getting into the cylinders or bolt holes. In replacing the cylinder head gasket turn the motor over so that No. 1 and No. 4 pistons are at top center; place the gasket in position over the pistons and then put the cylinder head in place. Be sure and draw the cylinder head bolts down evenly (i. e., give each bolt a few turns at a time). Do not tighten them on one end before drawing them up at the other.

Q. How are spark plugs cleaned?

A. After removing the plug from the engine the points may be cleaned with an old tooth brush dipped in gasoline. However, to do the work thoroughly, the plug should be taken apart by securing the large hexagon steel shell in a vise and loosening the pack nut which holds the porcelain in place. The carbon deposits can then be easily removed from the porcelain and shell with a small knife. Care should be exercised not to scrape off the glazed surface of the porcelain, otherwise it will be apt to carbonize quickly. The porcelain and other parts should be finally washed in gasoline and wiped dry with a cloth.

In assembling the plug care should be taken to see that the pack nut is not tightened too much so as to crack the porcelain, and the distance between the sparking points should be ¹⁄₃₂″, about the thickness of a smooth dime. Dirty plugs usually result from an excess of oil being carried in the crank case, or from using oil of poor quality.

Q. How is the power plant removed from the car?

A. (1) Drain the water out of the radiator and disconnect the radiator hose. (2) Disconnect the radiator stay rod which holds it to the dash. (3) Take out the two bolts which fasten the radiator to the frame and take radiator off. (4) Disconnect the dash at the two supporting brackets which rest on the frame. (5) Loosen the steering post bracket, fastened to the frame, when the dash and steering gear may be removed as one assembly, the wires first having been disconnected. (6) Take out the bolts holding the front radius rods in the socket underneath the crank case. (7) Remove the four bolts at the universal joint. (8) Remove pans on either side of cylinder casting and turn off gasoline; disconnect feed pipe from carburetor. (9) Disconnect exhaust manifold from exhaust pipe by uncovering large brass pack nut. (10) Take out the two cap screws which hold the crank case to the front frame. (11) Remove the bolts which hold the crank case arms to the frame at the side. Then pass a rope through the opening between the two middle cylinders and tie in a loose knot. Through the rope pass a “2 by 4,” or stout iron pipe about ten feet long, and let a man hold each end; let a third man take hold of the starting crank handle, when the whole power plant can be lifted from the car to the work bench for adjustment.

Q. How are the connecting rod bearings adjusted?

A. Connecting rod bearings may be adjusted, without taking out the engine, by the following method: (1) Drain off the oil; (2) Remove plate on bottom of crank case, exposing connecting rods; (3) Take off the first connecting rod cap, and drawfile the ends a very little at a time; (4) Replace cap, being careful to see that punch marks correspond, and tighten bolts until it fits shaft snugly; (5) Test tightness of bearing by turning engine over with the starting handle. Experienced mechanics usually determine when the bearing is properly fitted by lightly tapping each side of the cap with a hammer; (6) then loosen the bearing and proceed to fit the other bearings in the same manner; (7) after each bearing has been properly fitted and tested, then tighten the cap bolts and the work is finished.

Remember that there is a possibility of getting the bearings too tight, and under such conditions the babbitt is apt to cut out quickly, unless precaution is taken to run the motor slowly at the start. It is a good plan after adjusting the bearings to jack up the rear wheels and let the motor run slowly for about two hours (keeping it well supplied with water and oil) before taking it out on the road. Whenever possible these bearings should be fitted by an expert Ford mechanic.

Worn connecting rods may be returned, prepaid, to the nearest agent or branch house for exchange at a price of 75 cents each to cover the cost of rebabbitting. It is not advisable for any owner or repair shop to attempt the rebabbitting of connecting rods or main bearings, for without a special jig in which to form the bearings, satisfactory results will not be obtained. The constant tapping of a loose connecting rod on the crank shaft will eventually produce crystallization of the steel, resulting in broken crank shaft and possibly other parts of the engine damaged.

Q. How are the crank shaft main bearings adjusted?

A. Should the stationary bearings in which the crank shaft revolves become worn (evidenced by a pounding in the motor) and need replacing or adjustment, proceed as follows: (1) After the engine has been taken out of the car, remove crank case, transmission cover, cylinder head, pistons, connecting rods, transmission and magnetic coils. Take off the three babbitted caps and clean the bearing surfaces with gasoline. Apply Persian blue or red lead to the crank shaft bearing surfaces, which will enable you, in fitting the caps, to determine whether a perfect bearing surface is obtained.

(2) Place the rear cap in position and tighten it up as much as possible without stripping the bolt threads. When the bearing has been properly fitted, the crank will permit moving with one hand. If the crank shaft cannot be turned with one hand, the contact between the bearing surface is evidently too close, and the cap requires ohming up, one or two brass lines usually being sufficient. In case the crank shaft moves too easily with one hand, the shims should be removed and the steel surface of the cap filed off, permitting it to set closer.

(3) After removing the cap, observe whether the blue or red “spottings” indicate a full bearing the length of the cap. If “spottings” do not show a true bearing, the babbitt should be scraped and the cap refitted until the proper results are obtained.

(4) Lay the rear cap aside and proceed to adjust the center bearing in the same manner. Repeat the operation with the front bearing, with the other two bearings laid aside.

(5) When the proper adjustment of each bearing has been obtained, clean the babbitt surface carefully and place a little lubricating oil on the bearings, also on the crank shaft; then draw the caps up as closely as possible, the necessary shims, of course, being in place. Do not be afraid of getting the cap bolts too tight, as the shim under the cap and the oil between the bearing surfaces will prevent the metal being drawn into the close contact. If oil is not put on the bearing surfaces, the babbitt is apt to cut out when the motor is started up before the oil in the crank case can get into the bearing. In replacing the crank case and transmission cover on the motor, it is advisable to use a new set of felt gaskets to prevent oil leaks.