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(43)
ENGINE
TROUBLE DIAGNOSIS
2-21
mum pressure. If the pressure is built up in the
gauge in jerky steps of 10 or 20 pounds at a
t
ime,
it indicates leakage of pressure at some point
such as head gasket, valves,
or
piston rings.
(f) Normal compression pressure at crank-
ing speed is approximately as follows, in an
engine which is fully broken in.
Series 40
112 lbs.Zsq. in.
Series 50-70, Syncro-Mesh .. 114 lbs.Zsq. in.
Series 50-70, Dynaflow ..... 118Ibs.jsq. in.
Pressure variation between all cylinders
should not exceed 6 lbs.jsq. in.
(g) Low compression pressure in two adja-
cent cylinders indicates a head gasket leak be-
tween the two cylinders.
(h) If one or more cylinders have low com-
pression pressure or there is considerable varia-
tion between cylinders, inject
S.A.E.
20 engine
oil (not over 1 tablespoon full) into each low-
reading cylinder. Crank the engine a few rev-
olutions and recheck the compression pressure.
A material increase in pressure indicates that
compression is being lost past the pistons and
rings, whereas no increase in pressure indicates
sticking or poorly seating valves.
7. Check valve lash and adjust as necessary
(par. 2-14).
8. Clean strainers in fuel pump and carbu-
retor inlet (par. 3-9)
.
9. Inspect and test fuel pump (par. 3-17).
10.
.
Free up and lubricate manifold heat
valve (par. 3-11)
.
11. Clean and refill air cleaner (par. 3-8).
12. Check operation of choke valve and set-
ting of choke thermostat (par. 3-13).
13. Check adjustment of fast idle cam and
choke unloader (Carter par. 3-23; Stromberg
par. 3-30).
14. Check timing of accelerator vacuum
switch
if
starting
difficulty is experienced (Car-
ter par.
10-32;
Stromberg
par.
10-33).
15. Check throttle linkage
ad
j ustment
(p
ar .
3-10) .
16. Adjust carburetor (par.
3-12 ).
17. Adjust fan belt (par. 2-27).
18. Inspect all water hose connections and
tighten clamps.
19. Road test car for power and overall per-
formance.
2-1
0
EXCESSIVE VALVE NOISE
a. Excessive Noise with
Ad just a ble
Valve
Lash M
echanism
With the va
lves lashed
uniformly t
o
speci-
ficat ions, the noise level
should
be very low as
observed in the car while driving. The sound
of valve action will be audible, however, when
the hood is raised or when the engine is operat-
ing on fast idle during warm up.
The valve lash must not be reduced below
specifications in an attempt to eliminate valve
noise, as this will cause formation of carbon
on valve seat and stems which will then in-
crease valve noise and lower the engine per-
formance. Burned or warped valves will result
from insufficient lash clearance.
The following conditions generally cause ex-
cessive valve noise
:
(1)
Excessive or Uneven Valve Lash Clear-
ances. Adjust valve lash (par. 2-14).
(2)
Insufficient Oil to Valve Mechanism.
Check piping, restricted fittings, and oil line
screen (when used) to remove any obstruction
to proper flow of oil to rocker arm shaft.
(3)
Sticking Valves. Sticking valves are usu-
ally indicated by an intermittent loudness of
action, although valves will be unusually noisy
at all times if they are sticking badly. Sticking
valves will cause irregular operation or missing
on a low-speed pull. Recondition valves (par.
2-17) .
(4)
Warped or Eccentric Valves, Worn
Guides.
Check valves and replace if necessary.
Install new val
ve
guides if worn. See para-
graph 2-17.
(5)
Worn or Scored Parts in Valve Train.
Inspect rocker arms, ball studs, push rod ends,
push rods for bends, valve lifters, and camshaft
for worn or scored wearing surfaces. Replace
parts as required.
b. Excessive Noise with Hydraulic Valve
Lifters
NOTE: When an engine equipped with hy-
draulic valve lifters has been standing for con-
siderable time (such as overnight) some valve
noise will occur when engine is first started.
This is because oil escapes from the lifters that
are
holding
valves open against valve spring
pressure. These lifters will fill with oil and
noise will
disappear
after a f
ew
seconds of
runmina
,
Th
is
conditi on
must
not be classed as
excessiv e valve noise.
To locat e a noisy valve lifter remove the
rocker arm cover. With engine idling place a
finger on each valve spring cap in succession. A
distinct shock will be felt when the valve re-
turns to its seat if a valve lifter is not func-
tioning properly. The valve will return to its
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