1.6 Piston and Piston Rings
DETROIT DIESEL 53
Select a feeler gage with a thickness that will require a pull of six pounds to remove. The clearance will be .001 " greater
than the thickness of the feeler gage used, i.e., a .004" feeler gage will indicate a clearance of .005 "when it is withdrawn
with a pull of six pounds. The feeler gage must be perfectly flat and free of nicks and bends.
If any bind occurs between the piston and the liner, examine the piston and liner for burrs. Remove burrs with a fine
hone (a flat one is preferable) and recheck the clearance.
Fitting Piston Rings
Each piston is fitted with a fire ring, three compression rings and two oil control rings (Fig. 1). The current top
compression (fire) ring can be identified by the bright chrome on the bottom side and oxide (rust color) on the top. The
former ring had a plain metal color on both sides. A two-piece oil control ring is used in both oil ring grooves in the
pistons for non-turbocharged (naturally aspirated) engines.
All new piston rings must be installed whenever a piston is removed, regardless of whether a new or used piston or
cylinder liner is installed.
Insert one ring at a time inside of the cylinder liner and far enough down to be within the normal area of ring travel. Use
a piston to push the ring down to be sure it is parallel with the top of the liner. Then measure the ring gap with a feeler
gage as shown in Fig. 9. Refer to Section 1.0 for ring gap specifications.
If the gap on a compression ring is insufficient, it may be increased by filing or stoning the ends of the ring. File or stone
both ends of the ring so the cutting action is from the outer surface to the inner surface. This will prevent any chipping or
peeling of the chrome plate on the ring. The ends of the ring must remain square and the chamfer on the outer edge
must be approximately .015"
Check the ring side clearance as shown in Fig. 10. Ring side clearances are specified in Section 1.0.
Install Piston Rings
Before installing the piston rings, assemble the piston and rod as outlined under Assemble Connecting Rod to
Piston in Section 1.6.1. Then refer to Fig. I 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. 2. 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 with the tapered
face, be sure the side marked "TOP" is toward the top of the piston.
2. Stagger the ring gaps around the piston.
OIL CONTROL RINGS
The upper and lower oil control rings used on pistons for non-turbocharged engines consist of two halves (upper and
Install the oil control rings as follows:
1. Install the ring expanders in the oil control ring grooves in the piston.
CAUTION: When installing the oil control rings, use care to prevent
overlapping the ends of the ring expanders. An overlapped expander will
cause the oil ring to protrude beyond allowable limits and will result in
breakage when the piston is inserted in the ring compressor during installation
in the cylinder liner. Do not cut or grind the ends of the expanders to prevent
overlapping. Cutting or grinding the ends will decrease the expanding force on
the oil control rings and result in high lubricating oil consumption.
Install the upper and lower halves of the lower oil control ring by hand. Install the upper half with the gap 180° from the
gap in the expander. Then install the lower half with the gap 45° from the gap in the