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Fit. 62-UPfKr
J~rtilifl'lf
ShUld Rontwetl
6. Compression on all cylinders should be 130 pounds or
better. All cylinders should read alike within 5 to 10
pounds for
satisfactory engine
performance.
Should a low compression
reading
be
obtained
on
two
adjacent
cylinders,
it indicates the possibility of
a
leak from
one cylinder to the other, usually caused by
a
Jeak
at
the
cylinder head gasket.
If tbe compression readings are low, or vary widely, the
cause
of
the trouble
may be
determined by injecting a
liberal supply
of engine
oil on top
of
the pistons of the low
readiog
cylinders.
Crank
the
engine over several
times, and then take a
second
compression
lCSt.
If
there is practically no difference
in
the readings when
compared
with the first Aest,
it
indi·
40
cates sticky or poorly seating valves. However,
if
the
pression on the low reading cylinders is higher
and
a
uniform with the other cylinders it
indicates compf'ClSi
loss past the pistons and rings.
The
cause of
low or
uneven compression
must
be
correc~
before proceeding with an
engine
tune-up job.
SPARK PLUGS
To gain
access
to the spark
plugs, the upper ignition shid
(fig. 61) must be removed. It
is
important
that this shiel
be replaced when servicing
is
complete.
Clean the spark plugs thoroughly
using an abrasive
t
cleaner.
If
the porcelains
are
hadly
glazed or blistered,
th
F't. 63-SeU;ng Spark
Plug
Gop
spark
pi
ugs
should
replaced. AU spark
plu~
must be of the same roak
and number or heat rang
Adjust
the spark plug ga
to .035' using a round
feeler
gauge
(fig.
63)
.
CAUTION
:
In adjwtin
the spark plug gap,
never
bend
the
center.
electrode which ex
tends through the
porcelain
center.
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