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Chapter 19 Engine Reassembly and Break-In
thickness with the amount of gap specifi ed. If the
gap is too small, it can be corrected by carefully
fi ling the ring ends. See Figure 19-10. If the gap is
too wide, a new ring is required.
Installing Rings
If the piston ring-to-groove side clearances and
end gaps are satisfactory, install the rings on the
piston. Refer to the instructions that came with
the ring set to determine how the rings should be
installed. Generally, if the rings have a chamfer
on the inside edge, the ring is installed with the
chamfered edge up.
The oil control ring is installed fi rst, into the
bottom groove of the piston. The oil control ring
may be a one-piece unit or a three-piece unit con-
sisting of two thin rails and an expander. One-
piece oil control rings are installed using a ring
expander, and three-piece rings are installed
by hand. The expander is installed fi rst, then
the rails are installed one at a time. The rails
are installed in the top ring groove, and then
twisted down, one groove at a time until they
are in position on either side of the expander.
See Figure 19-11.
The two compression rings are installed next.
See Figure 19-12. The rings should be rotated so
the ring gaps are staggered 120°. Next, lubricate the
rings and piston skirt heavily with clean engine
oil. Do not apply assembly lube to the rings and
piston skirt.
Installing the Piston and Rod Assembly in
the Cylinder
Next, tighten a piston ring compressor
around the piston head to compress the rings
fl ush with the grooves. See Figure 19-13. Hold
the compressor fi rmly against the top of the
block and use a wooden dowel or hammer han-
dle to tap the piston out of the compressor and
into the cylinder. Once free of the compressor,
the rings will maintain fi rm contact with the
Figure 19-10.
Ring ends can be dressed with a fi le if the end gap is
too small. Use copper vise jaws to protect the ring.
Figure 19-11.
If the oil control ring is a three-piece design, install
the expander fi rst. Then, twist the rails into place one
at a time.
Figure 19-12.
Install the compression rings. Stagger the ring gaps by
120° to prevent blowby.