How To Rebuild Your Ford V-8 351C-351M-400-429-460.pdf - Index of

DIAGNOSIS
home and dumping the "instant overhaul"
solution down the carburetor. This stuff
really works, loosening the carbon which
then causes these problems. Don't try the
"cure-all" approach to rid your engine of
carbon. Use the methods I discuss in the
block and cylinder-head reconditioning
chapter. Also, carbon is an effect rather
than a cause. It results from an excessively
rich fuel mixture, oil getting into the
combustion chamber past the piston or
intake-valve stem, very slow driving or
idling for extended periods. If carbonbuildup
causes are cured, the deposits
gradually burn away, negating any need
to tear your engine down to remove the
deposits mechanically.
DIAGNOSIS
Now that I've discussed the types of
internal problems you may encounter
with your engine and how each may affect
its operation, let's look at how to diagnose
these problems without tearing your
engine -down. On the other hand, your
engine may not have any specific problems,
but you do want to determine if
it's time to rebuild.
Internal Noises-Perhaps your engine has
noises of impending disaster coming from
its innards. They may or may not be
accompanied by an increase in fuel or oil
consumption or a reduction in power.
Generally, if the noise is at engine speedonce
for every revolution of the crank-the
problem is in the bottom end. Causes are
a broken piston ring, worn connecting-rod
bearing or a worn piston-pin bore
A noise at half engine speed or camshaft
speed, is probably in the valve train,
with one exception. Piston slap occurs
only on the power stroke, consequently it
is also at half speed. If the noise is coming
from the valve train, it could be due to
excessive lash or clearance in the valve
train caused by a collapsed hydraulic
lifter, too much valve clearance or a bent
pushrod. To help in determining the
speed of the noise, hook up your timing
light and watch the light whle listening
to your engine. If the light flashes in time
with the noise, it's at half engine speed.
To assist in listening to what's going
on inside your engine, use a long screwdriver
and press its tip against the block
or cylinder head close to the area where
you suspect the noise to be coming from.
Press your head, or skull just below your
ear against the handle. This will amplify
engine noises. Just make sure you place
the screwdriver against a solid part of the
engine to get the best noise transmittal.
Don't put the end of the screwdriver
against the valve cover when listening to
Noise-related engine problems can be located with an automotive stethoscope. You must
be able to distinguish between normal engine noises and those which are not.
valve-train noises. Put it against the head
or a valve-cover bolt. The cork gasket
between the cover and the head and the
large air space under the valve cover muffles
much of the noise.
What should the different noises sound
like Let's start with the bottom end. A
broken piston ring makes a chattering or
rattling noise which is more prevalent
during acceleration. A dull or hollow
sound is usually caused by piston slap, or
the piston wobbling and slapping against
the side of its bore due to excess clearanc,e
between the piston and bore. A collapsed
piston skirt causes a similar, but louder
noise. Slap resulting from excess clearance
will be loudest when the engine is cold. It
decreases as the engine warms up and the
piston grows to reduce piston-to-bore
clearance. You can check for piston slap
by retarding the spark. Loosen your distributors's
hold-down bolt and rotate it
counterclockwise about 5 degrees. This
will retard the spark and should reduce
any noise due to piston slap. Use your
timing light to reset your timing after
you've made this check.
A light knochng or pounding noise
that's not related to detonation or preig-,
nition is probably excess connecting-rodbearing-to-journal
clearance. Simply put,
the bearing is worn out. Finally, a light
tapping noise can indicate excess pistonpin
clearance in the piston.
To confirm and pinpoint a bottom-end
noise-related problem, disconnect the
spark-plug leads one at a time, then run
your engine and listen for the noise to
change or go away. What happens is the
power-stroke is eliminated from the
cylinder with the disconnected spark-plug
lead, thus unloading its piston and connecting
rod. So, if the noise is piston or
rod-related, it will be greatly reduced or
eliminated when you have the plug wire
disconnected from.the problem cylinder.
If your car is equipped with a solid-state
ignition, always ground the lead you disconnect.
Otherwise you risk damaging
your expensive ignition system.
A sharp clacking or rapping noise indicates
your engine probably has a collapsed
hydraulic lifter. If the noise is a light
cliclung, it is probably excess clearance in
one of the valve mechanisms. This assumes
your engine is not equipped with solid
lifters which click normally-unless the
cliclung is excessive. Then the problem
will also be excess clearance, or lash. If
SOL1 D-STATE IGNITION SYSTEMS
Many solid-state (electronic) ignition
systems generate very high secondaryvoltage
peaks when a spark-plug lead
is unloaded by disconnecting it from
its spark plug, or by disconnecting the
coil-to-distributor lead while the engine
is being cranked or is running.
The resulting secondary ,voltage surge
of up to 60,000 volts can damage a
coil internally, or pierce plug-wire insulation
or a distributor cap as the
high voltage seeks a ground. So, if you
remove any secondary lead with the
ignition on and the .engine turning,
ground the lead to the engine with a
jumper wire. Ford has installed solidstate
(breakerless) ignitions since 1974.
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