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

After you've cleaned out the head- and
main-bearing-bolt threads, go after the
water passages. Remove any loose rust,
deposits and core sand. Pay particular
attention to the passages connecting the
cylinder heads to the block to ensure
good coolant flow to the heads. A round
or rat-tail file works well for this iob. but
be careful of the head-gasket surtaces. A
gouge in the wrong place can cause aheadgasket
leak. Give the same treatment to
She cylinder heads
During all this scrubbing, scraping and
general clean-up, compressed air for forcing
dirt out of hard-to-get-at areas and for
drying the block will be a definite help.
Controlling moisture becomes more of a
problem as you recondition more and
more of the parts. Bearing-bore surfaces,
cylinder bores, valve seats and any other
machined surface will rust from humidity
in the air. So, prevent this by coating the
machined surfaces with a water-dispersant
oil after cleaning or machining. Several
brands are available from your local store,
such as WD-40 and CRC. They'll do
the job with a lot less fuss and mess than
a squirt can of motor oil. Whatever you
use, don't leave any freshly machined surface
unoiled or it will rust for sure
CYLINDER-BLOCK FINAL
INSPECTION & RECONDITIONING
Inspecting your engine block to determine
what must be done to restore it to
tip-top condition is your first reconditioning
step. To perform a satisfactory
inspection job, you'll need 3-4.-inch outside
and inside micrometers, a very
straight edge, and feeler gages. A set of
telescoping gages will eliminate the need
for the inside mikes. You may not need
the straight edge if the head-gasket
checked out OK. If the old gaskets didn't
leak, the new ones won't either, if they
are installed correctly.
Checking Bore Wear-Cylinder-bore wear
dictates whether your block needs boring
or just honing. This, in turn, largely determines
whether you have to install new
pistons-no small investment.
You can check bore wear three ways.
The best is with a dial-bore gage, but you
may not have one, so let's look at the remaining
methods. Next in order of accuracy
is the inside micrometer or telescopic
gage and an outside mike. The last method
involves using a piston ring and feeler
gages to compare end-gaps at different
positions in the bore. All of these methods
will tell you what each bore's taper is.
Bore Taper-Cylinder walls don't wear the
same from top to bottom. A bore wears
WEAR
(IN.)
CYLINDER-WALL WEAR VS OPERATING TEWIPERATURE
60-HOUR TEST
TEMPERATURE (OF)
Why you should always use a thermostat. Bore wear increases dramatically as engine
operating temperature goes down, particularly when it's less than 180°F (82°C). Data
courtesy Continental Motors.
more at the top, with wear decreasing toward
the bottom. Virtually no wear occurs
in the lower portion of a bore. Load exerted
by the top compression ring against
its cylinder wall during the power stroke
decreases rapidly as the piston travels
down from the top of its stroke. This
varying load is the major cause of bore
taper. In addition, the bottom of a bore
which has the maill function of stabilizing
the piston is better lubricated and receives
little wear. This is shown by the
shiny upper part of a bore-while the
bottom retains its original cross-hatch
pattern.
Measuring Taper-Because a bore wears
little at its bottom, if you compare the
distance across the bore at the bottom
versus that at the top, just below the
ridge, you can determine its taper. Also,
bores don't' wear evenly all the way
around, nor do all cylinders wear the
same. Therefore, when measuring a bore,
measure it parallel to the centerline of
the engine, then at 90" to the centerline.
Take a couple of measurements in between
and use the highest figure. It will
determine what and how much must be
done to that bore to restore it. Because
it's not practical to treat each cylinder
separately, you'll have to pinpoint the
one with the worst taper and let it be the
gage of what must be done to the remaining
seven cylinders. One exception is
when one cylinder is damaged or worn
beyond the point where it can't be re-
stored by boring, and the other cylinders
are OK. In this case, it may be less expensive
to have the cylinder sleeved rather
than junking your block and buying
another one.
When checking bore wear you'll notice
the end cylinders have the most wear.
The reason is the end cylinders operate
cooler than the others, causing more
wear. Most wear is concentrated on the
side of the cylinder walls closest to the
ends of the cylinder block in cylinders
1, 4, 5 and 8. A quick way to verify what
I've said is to compare the ridges in each
bore by feeling them with your finger tip,
particularly the variation in thickness of
the ridges in the end cylinders. Because of
the wear pattern in the end cylinders,
wear measured parallel to the engine centerline
will exceed that measured 90" to
the centerline.
Due to uneven bore wear, taper, or the
difference between maximum and minimum
bore wear, measuring may not provide
a final figure as to how much a cylinder
must be bored to clean it up-to
expose new metal the full length of a
bore. The reason is, uneven wear shifts a
bore's centerline in the direction of the
wear.
To restore a cylinder to its original
centerline usually requires removing more
metal than indicated by its taper. As a
result, final bore-size determination is
made at the time of boring. If a cylinder
bore does not clean up at 0.010 inch
oversize, the machinist has to bore to
I
BLOCK RECONDI.rIONING 53