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

file the end of the ring like the one shown
in the accompanying photo. Wrap tape
around the ring so you don't cut your
fingers on it.
Be careful, no matter which method
you use. Caution: Don't remove any metal
or scratch the grooves, just get rid of the
deposits. Be especially careful to avoid
removing metal from the side surfaces of
the grooves as they are the surfaces against
which the rings seal.
Measuring Ring-Groove Width-Again,
chances are if a ring groove is worn or
damaged, it will be the top one because
of its higher loads. So start with it. This
doesn't mean you don't have to check the
others if the top one is OK. Unforeseen
things can happen, check them Checking pin-bore wear by twisting con-
Look at the clean grooves first. Any wear necting rod in direction A, then trying to
will have formed a ster, on the lower por- rotate it in direction 6, 90" to its normal
tion of the ring land.-~he height of'the direction of rotation. If you can feel movement
at pin when holding piston like this,
step up as ring side dn-bore wear is excessive and the &ton
~ - - - - - - - - - -
clearance and the length of the step pro- ;hould be redaced.
jecting from the back-wall of the groove
represents the piston ring's back-clearance.
Side clearance between one side of the
ring and a ring land is measured with a
ring and feeler gage with the ring held
against the opposite ring land. If it is too
much, proper ring-to-piston sealing is not
possible, plus the additional action of the
ring moving up and down in the groove
will accelerate wear and increase the
possibility of breaking a ring land.
Start cleaning your pistons by removing
carbon from their tops. A dull screwdriver
is good for removing big chunks and a wire
brush does cleanup work, but don't touch
piston sides with the brush. A piston can
easily be ruined by careless wire brushing.
Compression-Ring Grooves-Compressionring
grooves are nominally 0.080-inch
wide, new rings have a minimum 0.077-
inch width and a maximum ring side clearance
of 0.006 inch. You are presented
with a dilemma because the 0.006-inch .+
side clearance should be measured with a TWO tools which accomplish the same thing-an official ring-groove cleaner or a broken
piston ring ground like this. Ring is harder to use, but a lot cheaper. Regardless of how you
new ring in the groove. You don't want clean your ring grooves, be careful not to remove any metal.
to lay out money for a new set of rings
for checking your old pistons until you've
checked them and have given them the new ring. In formula form, this looks using this method. Make sure the ring is
OK. One way around this is to use an old like:
not up on the step when checking side
ring for checking. The problem is, rings
Maximum checking clearance
clearance.
wear too, and more than actual side clearance
will show up if ring wear is not
= 0.006 + (0.077- 0.076) or:
accounted for. J~~~ mike the old ring and
Maximum checking clearance in inches
subtract this amount from 0.077 inch,
= 0.006 + (0.077- checking-ring
the minimum width of a new compres- width in inches)
sion ring. Add this figure to 0.006 inch When checking side clearance, insert
for the maximum allowable checking the edge of the ring in the groove with
clearance. I'll use the term checking the checking-clearance feeler gage alongclearance
rather than side clearance be- side between the ring and the lower side
cause the gage thickness may not be the of the ring groove. Slide the gage and
actual side clearance with a new ring. If ring completely around the groove to
the old ring measured 0.076 inch, it is check for any clearance variations and to
0.001-inch undersize. Consequently, verify the land is free from distortion or
maximum checking clearance is now uneven wear. The gage should slide the
0.007 inch but it will yield a 0.006-inch full circumference without binding.
side clearance with a minimum-width Check both compression-ring grooves
Oil-Ring Grooves-Nominal oil-ring
grooves are 0.1885-inch wide. The real
test is a snug fitting oil ring. Here's that
old problem again. You don't yet have
a new set of rings to do the checking.
Fortunately oil rings and their grooves are
well lubricated and aren't heavily loaded
like the compression rings, particularly
the top one. Consequently, their wear is
minimal, so if they pass your visual inspection
you can assume they are all right.
However, to be positive, measure them.
To do this, stack two old compression
rings together and mike their combined
thickness.