Advertisement
2-40
PISTONS-RODS
ENGINE
(62)
be honed to remove glaze when the second set
of rings is installed.
e. Fitting New Piston Rings
When new piston rings are installed without
reboringcylinders, the glazed cylinder walls
should be slightly dulled, but without increas-
ing the bore diameter, by means of the finest
grade of stones in a cylinder hone.
New piston rings must be checked for clear-
ance in piston grooves and for gap in cylinder
bores; however, the Flex-Fit rings are not
checked for gap. The cylinder bores and piston
grooves must be clean, dry and free of carbon
and burrs.
Check the clearance of each ring in its piston
groove by installing the ring and then inserting
feeler gauges under the ring. Any wear that
occurs in the piston groove forms a step or
ridge at inner portion of the lower land. If
gauges are inserted above the ring, the ring
may rest on the step instead of on the worn
portion of the lower land, and a false measure-
ment of clearance will result.
If
the piston grooves have worn to the
ex-
tent that relatively high steps or ridges exist on
the lower lands, the piston should be replaced
because the steps will interfere with the opera-
tion of new rings and the ring clearances will
be excessive. Piston rings are not furnished in
oversize widths to compensate for ring groove
wear.
Piston rings should have not less than .0015"
nor more than .004" clearance in
piston
grooves.
To check the gap of rings other than Flex-
Fit, place the ring in the cylinder in which it
will be used, square it in the bore by tapping
with the lower end of a piston, then measure the
gap with feeler gauges. Piston rings should not
have less than .010" gap when placed in cylin-
der bores. If gap is less than .010", file the ends
of rings carefully with a smooth file to obtain
proper
gap.
f. Assembly and Installation of Piston and
Connecting Rod Assemblies
1.
Connecting rods may be sprung out of
alignment in shipping or handling,
therefore,
they must always be checked before pistons are
installed.
Clamp a new piston pin in upper end
of connecting rod and test the rod for twist
and bend, using an accurate connecting rod
aligning fixture. See figure 2-37. Bend or twist
the rod if necessary, to secure proper align-
ment.
Figure 2-37-Checking Connecting Rod Alignment
2. Install the piston and pin on connecting
rod with the hollow side of piston head on same
side as the small oil hole in rod. Tighten the
piston pin clamp bolt securely. Do not clamp
the rod in a vise for this operation as the rod
may be sprung out of alignment when tighten-
ing clamp bolt, or if vise jaws are not square.
3. Check alignment of rod and piston in the
connecting rod aligning fixture. See figure 2-38.
4. Install channeled oil ring in third groove
and compression rings in second and first
grooves of each
piston.
Be sure to place the
grooved or beveled side of compression rings
Figure 2-38-Checking Connecting Rod and Piston Alignment
Advertisement
