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12 THE FORD M A N U A L
tion indicated in Cut No. 3. The opening and closing of the valves being 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 cylinder casting measuring
3 3-8". The exhaust valve will close on top center, the piston being 5-16" above
the cylinder casting. The intake valve opens 1-16" after 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 3 1-8".
How the valve lifting tool should be used. (Cut No. 4)
The clearance between the push rod and valve stem should never be greater than
1-32" nor less than 1-64". The correct clearance is naturally half
way between these two measurements. The gap should be measured when the push
rod is on the heel of the cam.
What about the
care of the Valves? Answer No. 23
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 a lack of resistance in one or more cylinders, it is probable that the valves
need re-grinding. As the "life" of the engine depends largely upon
the proper seating of the valves, it is necessary that they be ground occasionally.
How are Valves removed
for grinding? Answer No. 24
(1) Drain radiator; (2) remove cylinder head; (3) remove the valve cover on the
right side of engine; (4) raise the valve spring with lifting tool (see Cut No.
4) and pull out the little pin that is in the valve stem. The valve may then
be lifted out by the head.
How are Valves ground? Answer No. 25
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 smooth and bright. The valve should not be turned
through a complete revolution, 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 re-moved 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 to the bevel face of the valve.
If the valve seat is worn badly or seamed, 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.
When the Valves and Push Rods are worn —what?
When the valves or 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 rods and the valve stem should never be greater than 31z" nor
less than A". 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 84" 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 requires experience and the price of the new part
does not warrant the time and expense necessary to properly do the work.
What about the
Valve Springs? Answer No. 27
When the valves fail to seat themselves properly, there is a possibility that
the springs may be weak or broken. Weakness in the exhaust valve spring causes
a very uneven action. The symptoms are a lag in the engine due to the exhaust
valve not closing instantaneously, and as a result a certain percentage of
the charge under compression escapes, greatly diminishing the force of the
Method of grinding valve. (Cut No. 5)
Answer No. 26