using new rings and a feeler gauge as shown in Figure
56.
See Dimensions and Clearances for proper side
clearance measurement and ring groove widths.
FIGURE 56. RING LAND INSPECTION
Improper width rings or excessive ring side clearance
can result in ring breakage. New rings in worn ring
grooves don't havegood cylinder wall contact (Figure
57).
CYLINDER
WALL
IMPROPER^
RING
CONTACT:
FIGURE 57. NEW RING IN WORN RING GROOVE
Replace pistons showing signs of bad scoring or
burring,
excessive skirt clearance, wavy or worn ring
lands,
fractures or damage from detonation. Replace
piston pins showing fractures, scored bores or bores
out of round more than 0.002-inch.
Use a new piston pin to check the pin bushing in the
connecting rod for wear. The clearance should be as
shown in Dimensions and Clearances.
Before installing new rings on the piston, check the
ring gap by placing each ring squarely in its cylinder,
at a position corresponding to the bottom of its travel
(Figure 58). The gap between the ends of the ring is
given in Dimensions and Clearances. Rings which are
slightly oversize may be filed as necessary to obtain
the correct gap, but do not use rings which require too
much filing. Standard size ringsmaybeusedon .005"
oversize pistons. Rings that are .010", .020", .030"
and .040" oversize are to be used on corresponding
oversize pistons. Ringsof thetapered type are usually
marked fop on one side, or identified in some other
manner and the ring must be installed with this mark
toward the closed end of the piston.
PISTON RING IN
\ CYLINDER BORE
ELER GAGE
FIGURE 58. FITTING PISTON RINGS TO THE CYLINDER
Engines that have been fitted with .005" oversize
pistons at the factory are identified by the letter
E
after
the serial number which is stamped on the cylinder
block and on the unit nameplate.
The standard cylinder bore size appears in
Dimensions and Clearances.
Space each ring gap one third of the way around the
piston from the preceding one, with nogapdirectly in
line with the piston pin. The bottom piston ring groove
should be fitted with an expander and an oil control
ring and the two upper grooves fitted with compres-
sion rings. If a chrome faced ring is used, it will be in
the top groove. Theoil control ring is selected forbest
performance in regard to the correct unit pressure
characteristics.
The piston is fitted with a full-floating type piston pin.
The pin is kept in place by two lock rings in the piston,
one at each side. Be sure these lock ringsare properly
in place before installing the piston and connecting
rod in the engine. Refer to Dimensions and
Clearances for the correct piston-to-cylinder
clearance.
38
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