The Washington herald., 1920-05-09
HOW TO REDUCE
VALVE TROUBLE
Cranking Engine by Hand
Way to Tell Com
preston Loss.
MUST WATCH LEAKS
After Testing for Defects
Springs Should Be
Examined.
MUST WATCH LEAKS

When poppet valves do not func-
tion properly due to warped heads,
pitted faces, bent stems, worn stems,
Ietc.. there is a considerable falling
lon in the power developed by the
engine and the owner Immediately
discovers it in the form of poor per-
formance. The time honored method
Of testing the compression by crank
ing the engine by hand slowly to
determine the relative resistance Of
fered, Is a fairly satisfactory way of
determining compression loss, but
does not indicate where that loss
exists. The owner OF a car should
bear in mind that valve heads work
in an extremely hot atmosphere,
since the heads are in the combus-
tion chamber and consequently are
Iexposed to the flame of the explo-
sions They must, therefore, be able
to Withstand the terrific heat with
out warping. because II they should
warp the effectiveness of the valve
to make perfect joint with its seat
would at once be destroyed The
reason car manufacturers state that
valves are surrounded by adequate
water space" is because they wish
to show that the valves being prop
erly cooled are not likely to be af-
fected very quickly by the heat. In
some engines where provision has
not been made for the proper cool
ing of the valves the engines give
continual trouble from loss of COM
preston, valves sticking, valves re-
curing frequent grinding, misfirins
due to irregularities in the valve ac-
tion, etc.
The only safe way an owner can
tell whether a valve head is warped
or badly pttted or a stem bent or
badly carbonized is to remove the
valve examine it and measure 1t.
While the compression test lis all
rlght to check losses due to poor
VaIVe seating, 1t must first be de-
termined that there is no leakage
elsewhere. as for example, around
the cylinder head Joint or valve
plugs If such be used. or past DOOR
ly fitting pistons or rings, or due to
worn cylinders, etc.
After valve Is removed by means
of a valve spring compressor ner-
mitting the valve seat support IN he
slipped out, 1t should first be care
fully cleaned by immersion i'm kero-
sene, then wiped with a clean cloth
Examine the face Of the valve for
small black spots. Place the valve
upright on level surface and meas
ure four or five distances from head
TO plate. This will give you a good
check on the trueness of the had
A variation that can be measured
with an ordinary rule may be taken
as being enough to cause poor valve
seating, hence leakage of mixture
past the valve when 1t is closed
valve with a warped head should be
replaced.
Test the stem for straiRhtness.
Place the stem on a level niato
while the head of the valve bangs
over the edge of the plate. The eve
can instantly detect IL the stem is
not straight. II it is bent a little n
may be Strengthened in a wise. A
bent stem may cause the valve to |
stick open or 1t also may cause n |
to return to Its seat too slowly. II l
the valve stem is straight IL should
be checked for diameter. The hest
way to do this is first to polish the
stem with a piece Of emery cloth
and then try 1t in its particular
guide. Place 1t in the guide (when
The tappet Is all the way down.
and holding one hand on the stem
md the other on the head Ito force
he valve against its seat) feel for
'ide play. There should be nonej
II the valve stem can
in Its guide It will allow
,il to leak down and air to leak I'M.
some of you may notice that there
s oil all around the valve springs
md the tappets and on the side Of
he engine on which the valves are
ocated. That oil usually comes out
through the valve guides, which. by
he way, may themselves be worn.
I is possible In some cases where
detachable guides are used to install
! new guide to fit the worn stem,
tut where this construction Is not
ised a valve with an oversize stem !
must be obtained and, lifted to the
Euide. Il should be just free enough
o It falls to its seat after being
fitted about an inch.
At the fir,aa fh.&p.r.