Figure 3-29.Tighten bolts in proper sequence.
from becoming warped by storing it on end in a
There are certain limits to which cylinders may
become tapered or out of round before they
require refinishing. If they have only a slight taper
or are only slightly out of round (consult the
manufacturers manual for the maximum allow-
able taper or out of round), new standard rings
can be installed.
When cylinder wear goes beyond the point
recommended in the engine manufacturers speci-
fications, loss of compression, high oil consump-
tion, poor performance, and heavy carbon
accumulations in the cylinder will result. In such
cases, the only way to put the engine back into
good operating condition is to refinish the
cylinders and fit new pistons (or oversized pistons)
CYLINDER WALLS CHECK
As a first step in checking cylinder walls, wipe
them clean and examine them carefully for scored
places and spotty wear (which shows up as dark,
unpolished spots on the walls). Holding a light
at the opposite end of the cylinder from the eye
will help in the examination. If scores or spots
are found, you should refinish the cylinder walls.
Next, measure the cylinders for taper and oval
wear. This can be done with an inside micrometer
or by a special dial indicator, as shown in figure
3-30. As the dial indicator is moved up and down
in the cylinder and turned from one position to
another, any irregularities will cause the needle
to move. This will indicate how many thousandths
of an inch the cylinder is out of round or tapered.
The permissible amount of taper or out of
roundness in a cylinder varies somewhat with
different engines. Engine manufacturers issue
Figure 3-30.Dial indicator for measuring cylinders.
recommendations based on experience with their
own engine. When the recommendations are
exceeded, the cylinders have to be refinished.
There are two methods of refinishing
cylinders: honing and boring. Cylinders are
refinished by honing when wear is not too great;
otherwise, they are bored with a machine, and
oversized pistons and rings are installed. This
machine consists of a boring bar and cutting tool,
and operating the boring machine will vary among
different makes of equipment. Consult the manu-
facturers operating manual for the procedures