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

Section of an oil-ring assembly. Left drawing shows how the expander-spacer fits behind
the two rails to spring-load them against the cylinder bore. Ends of a correctly installed
expander-spacer must butt (arrow), as shown in right drawing. Courtesy Sealed Power
Corporation.
Locate ring end gaps like this prior to comincludes
a small flat file, a ring com- rings for replacement. If a gap is too small, pressing them for installing the piston-and-
'Od
pressor. hammer. a large tomato can con- it can be corrected by filing or grinding your engine.
taining about a half quart of clean motor
oil, an oil can and some rod-bolt bearingjournal
protectors. You should consider
a ring expander too, even though it's
possible to install the rings without one.
The expander ensures the pistons won't
get scratched or the rings bent or broken
during the installation. If you can't
readily pick up a couple of bearingjournal
protectors, two 2-inch lengths of
318-inch rubber hose will work.
Gap Your Rings-Piston rings are manufactured
to close tolerances to fit specific
bore sizes, however, you should
check their end gaps just the same. Just
as with bearings, the wrong rings can
find their way into the right boxes. Once
they're on the pistons and in their bores,
you'll never know until it's too late. Also,
some high-performance piston rings must
be gapped.
Both compression rings should have a
0.010-0.020-inch end gap, or more precisely,
0.004-inch gap for each inch of
bore diameter. For example, compression
rings for a 4-inch bore should be gapped
at 0.004 x 4 = 0.016 inch. However, if
your ring gaps are in the 0.010-0.020-
inch range, they'll be all right. Gap range
for the two oil-iing side rails is much
wider at 0.015-0.055 inch.
To check a piston ring's end gap, install
it in a cylinder bore. Carefully fit the
ring in the bore and square it with an old
piston or a tin can. There's no need to
hush the ring down the bore more than a
half-inch unless your block hasn't been
rebored. In this case you should push the
ring at least 4 inches down the bore. The
reason is taper in a cylinder causes a ring
to close near the bottom of the stroke
and minimum end-gap-clearance should
be checked to prevent the ends of a ring
from butting when the engine is at maximum
operating temperature. If any gaps
are too large, return the complete set of
-
the end of the ring.
When filing or grinding a piston ring,
the first rule is to file or grind the end of
the ring with the motion from its outside
edge toward its inside edge. Ths is
particularly important with moly rings.
The moly filling on the outside periphery
will chip or peel off from the outside
edge. When filing, don't hold the ring
and file in your hands, clamp the file in
a vise or onto a bench with a C-clamp or
Vise-Grip pliers and move the ring against
the file. You'll have better control using
this method. For grinding a ring, use a
thin grinding disc, one that will fit be-
tween the two ends. Just make certain
the disc rotation grinds the end from the
outside in. Hold the ring securely so you
don't break it as you grind it.
Break the sharp edges from the ends
pip mark (arrow). when installing a
pression ring, make sure mark is toward
piston top.
Install the Rings on the Pistons-With
of any rings you filed or ground. Use a the rings gapped, you're ready to install
very-fine-tooth file or 400-grit sandpaper. the rings on their pistons. This can be
The inside edge will have the biggest burr, done without any special tools, but I
the outside edge the least-if any at all- recommend using a ring expander. It
and the sides will be somewhere in be- greatly reduces the possibility of ring or
tween. Just touch the edges with your piston damage during installation. An exfile
or sandpaper. Remove only enough pander is cheaper than another set of
material so you can't feel any sharp rings.
edges with your finger tips.
So you won't have to horse around
When you've finished one complete trying to hold a piston and rod while inring
set, keep it with the piston and rod stalling rings, lightly clamp each rod and
assembly that's to go in the bore you piston assembly in a vise. This will leave
used for checking and fitting. Repeat this your hands free to concentrate on inprocedure
until you've checked and stalling the rings. Clamp the rod between
fitted all the rings. It's best to keep the two small blocks of wood with the rod
rings in the envelopes they came in. The far enough down in the vise so the piston
ring manufacturer usually organizes the can't rock back-and-forth. Don't clamp
rings in sets with its rings in order-top on the piston. If you don't have a vise,
compression ring, second compression, make yourself comfortable by sitting
then the oil-ring assembly. Be careful down in a chair and clamp the rod and
not to get the rings mixed up, partic- piston between your knees. Installing
ularly the compression rings. The differ- rings this way is about as easy as using
ences between them are not readily a vise.
apparent, so it's best to keep the rings in Oil Rings-When installing rings on a
order to avoid installing them on the piston, start with the oil ring and work
piston in the wrong order.
up. You won't need the ring-expanding