.
A. Measure and record as
“A’
the cylinder bore
diameter (parallel to crankshaft) near the top
of cylinder bore where greatest amount of
wear occurs.
B.
Also
measure and record as“B” cylinder bore
diameter (parallel to crankshaft) at the bot-
tom of piston travel.
C.
Measure and record as
“C”
cylinder bore
diameter (perpendicular to crankshaft) near
the top of cylinder bore where greatest
amount of wear occurs.
D. Also measure and record as“D”cy1inder bore
diameter (perpendicular to crankshaft) at the
bottom of piston travel.
E.
Reading
“A’
subtracted from reading
“B
and
reading
“c”
subtracted from reading
“D
indi-
cates cylinder taper.
If cylinder taper exceeds that specified
in
DlMENSlONS
AND
CLEARANCES,
rebore and
hone cylinder to the next oversize.
F.
Reading
“A”
compared
to
reading
“C”
and
reading
“B
compared to reading
“D’
indicate
whether or not cylinder is out of round. If out of
round exceeds that specified in
DIMENSIONS
AND CLEARANCES,
the cylinders must be
rebored and honed to the next oversize.
A
reboring machine is used when going to oversize
pistons.
Reboring
the
Cylinder
Rebore and hone engine whenever cylinder bore is
worn, damaged, out of round, or if cylinder taper
exceeds specifications.
A
worn cylinder bore should
be resized to the smallest standard oversize diameter
at which it will clean up. The final finish and bore
diameters should then be obtained by honing.
E%{
AREA
TOP END
OF
CYLINDER
RING
.WEAR
AREA
BOTTOM
OF-RING
TRAVEL
c
1090
FIGURE
69.
METHODS
OF
MEASURING THE DIAMETER
OF
A
CYLINDER
BORE
If
boring bar
is
operatedincorrecfly,
if will produce
a
rough cylinder
sur-
face that may not clean up even when honed. Boring
should be done only
by
qualified service personnel
who
are careful in their
work.
After boring to the correct oversize cylinder bore
dimension piston and ring clearance should be
appropriate. There is no need to adjust or “fit” pistons
and rings.
When reboring cylinders, take the following pre-
cautions:
1.
Make sure cutting tool is properly ground before
2.
Besure top of engine block is smooth and deposit
using it.
free.
49
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