TM 5-3810-300-24-&P-3
Piston and Piston Rings 1.6
Before installing the piston rings, assemble the piston as
outlined under Assemble Connecting Rod to Piston in
Section 1.6.1. Then refer to Figs. 16 and 19 and install
the piston rings.
NOTE: Lubricate the piston rings and piston
with engine oil before installing the rings.
COMPRESSION RINGS
1. Starting with the bottom ring, install the compression
rings with tool J 8128 as shown in Fig. 16. To avoid
breaking or overstressing the rings, do not spread them
any more than necessary to slip them over the piston.
CAUTION: When installing the top
compression (fire) ring, be sure the black
Fig. 22 - Measuring Piston Ring Side Clearance
oxide or copper colored side (also identified
by an oval mark) is toward the top of the
To conform with this change, a tapered fire ring
piston.
(Fig. 20) must be used. The former piston
crown (17:1 compression ratio) had a
2. Stagger the ring gaps around the piston.
rectangular fire ring . groove. Only pistons with
OIL CONTROL RINGS
the tapered fire ring groove are available for
service.
The upper and lower oil control rings used on pistons for
non-turbocharged engines consist of two halves (upper
A two-piece oil control ring is used in both oil ring
and lower).
grooves in the pistons for non-turbocharged (naturally
aspirated) engines. A one-piece oil control ring in the
1. Install the ring expanders in the oil control ring
upper ring groove and a two-piece ring in the lower ring
grooves in the piston.
groove are used in the pistons for turbocharged engines.
CAUTION: When installing the oil control rings,
All new piston rings must be installed whenever a piston
use care to prevent overlapping the ends of ring
is removed, regardless of whether a new or used piston
expanders. An overlapped expander will cause
or cylinder liner is installed.
the oil ring to protrude beyond allowable limits
and will result in breakage when the piston is
Insert one ring at a time inside of the cylinder liner and
inserted in the ring compressor during
far enough down to be within the normal area of ring
installation in the cylinder liner. Do not cut or
travel. Use a piston skirt to push the ring down to be
grind the ends of the expanders to prevent
sure it is parallel with the top of the liner. Then measure
overlap-ping. Cutting or grinding the ends will
the ring gap with a feeler gage as shown in Fig. 21.
decrease the expanding force on the oil control
Refer to Section 1.0 for ring gap specifications.
rings and result in high lubricating oil
If the gap on a compression ring is insufficient, it may be
consumption.
increased by filing or stoning the ends of the ring. File or
IMPORTANT: When peripheral abutment type
stone both ends of the ring so the cutting action is from
ring expanders (Fig. 11) are used, install them
the outer surface to the inner surface. This will prevent
with the legs of the free ends toward the top of
any chipping or peeling of the chrome plate on the ring.
the piston. With the free ends pointing up, a
The ends of the ring must remain square and the
noticeable resistance will be encountered
chamfer on the outer edge must be approximately .015".
during installation of the piston if the ends of the
Check the ring side clearance as shown in Fig. 22. Ring
side clearances are specified in Section 1.0.
Install Piston Rings
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