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

Using a piston ring and a feeler gage for
checking ring-groove wear. New rings
should have no more than 0.006-inch side
clearance.
As an example, if the combined thickness
of two rings is 0.155 inch, and feelergage
thickness to get maximum oil-ringgroove
width, or 0.191 inch minus 0.155
inch = maximum allowable checking
feeler-gage thickness of 0.036 inch.
Maximum checking gage
thickness in inches
= 0.191 - Combined thickness of
two compression rings in inches
If the oil-ring grooves in your pistons
don't exceed this amount, you can be certain
the rings will fit snugly in their
grooves.
Now, use stacked rings with your feeler
gage to check groove width. You don't
have to install the rings in the groove.
Just inset their edges in the groove with
the gage and slide them around in the
groove as you did when checking the
compression-ring grooves.
Groove Inserts-If you have the unlikely
circumstance that your cylinders don't
need boring, only honing to get them
back into condition, and your pistons are
OK for reuse except for having too much
ring-groove wear, you can have your
piston-ring grooves machined wider. This
makes all the ring-groove widths consistent-and
larger. To compensate for the
additional clearance between the rings
and the grooves, ring-groove inserts are
installed-they are usually 0.060-inch
wide and are installed beside the rings. In
terms of cost, ridge-reaming and honing
your block, machining your pistons in
preparation for ring-groove inserts and
purchasing the rings and inserts will cost
50-60 percent of a rebore and new pistons
and rings. In this case, durability is
directly related to cost.You can expect
Using a connecting-rod alignment-checking
fixture to check for bent or twisted connecting
rods. When using this type of
checking fixture, the piston must be
installed on the rod. If a rod is found to be
out of alignment, it is straightened and then
rechecked.
approximately half the life from an engine
with inserted pistons compared to
one with a complete rebore job.
CONNECTING RODS
Inspecting connecting rods involves
checking three areas: out-of-round or
enlarged bearing bores, twisted or bent
rod beams and cracked rod bolts. Now's
when the old bearing inserts come in
handy. If a rod bearing shows uneven
wear from side-to-side-opposite sides
on top and bottom bearing halves-the
piston on that rod has wear spots offset
from its thrust face and the rod's crankshaft
bearing journal was not tapered,
the rod is bent, causing side loading.
With these symptoms, the rod and piston
assembly or assemblies should be taken
to an engine machine shop for accurate
checking and straightening if necessary.
Bearing condition also tells you if the
"big end" of the rod needs reconditioning.
When a rod is reconditioned the bearing
bore, or big end is checked with a special
dial indicator to determine its shaperound,
out-of-round or oversize. This is
basically the same thing you did with the
crankshaft bearing journals, however now
the check is made of the bore in which
the bearings are retained. With an outof-round
bore, its bearing inserts will
assume the same irregularity, causing
uneven load distribution between the
bearing and its journal, resulting in
uneven and accelerated bearing wear.
Consequently, the bore must be reconditioned.
A bearing with a too-large bore is even
worse. Oversize bearing bores will let
How much a bearing insert projects above
its bearing-bore parting line is called crush
height (about 0.001 inch). As bearing cap
is tightened down, the insert-half ends
contact first, forcing inserts to conform to
shape of bearing bore and to be locked in
place. This is called bearing crush.
bearings move in their bore-which is
not supposed to happen. The reason is
the insert halves are not sufficiently
crushed. Crush occurs when a bearing
cap is torqued, forcing the bearing to
conform to its bore. This is accomplished
by the combined outside diameter of
the two bearing insert halves being larger
than the ID of the bore. When a bearing
half is placed in its bore, its ends project
slightly above the bearing housing's parting
surfaces. Consequently, when two
bearing inserts are installed in their bore,
the ends of the inserts butt. As the
bearing-cap nuts are tightened, the two
circumferences must become equal. The
bearing shell ghes-is crushed-causing
the bearing to assume the shape of its
bore and to be preloaded, or fitted tightly
in its bore. This tight fit and the tooth,
or machining marks in the bearing bore,
combine to prevent the bearing inserts
from spinning-rotating in the bore rather
than the bearing journal rotating in the
bearing. This happens when the force at
the bearing journal which tries to rotate
the bearing overcomes the force between
the bearing and its housing, or bore
that is resisting this force. Consequently,
if the bearing bore is too large, the
bearing may move in the bore, or worse
yet, spin.
To determine if a bearing has been
moving in its bore, look at its backside.
Shiny spots on the back of the shell
indicate movement. If this happened,
either the bearing bore is too large
or the bearing-to-journal clearance was
insufficient. If you discover any shiny