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Page 12
Pistons and Connectlng Rods-conttnued
"'r
t
Fig. 1.2. Showing arrangement of piston rings.
I. Plain compression ring. 3. Laminatedcompressionring.
2. Chrome
plated
com-
4. and 5. Slotted
scraper
ring.
presaion
ring.
NOTE.
In the case of combine engines. the chrome
Dlated compression ring is omitted and replaced by a
plain compression ring of the same type as fitted in
No. 1 ring groove.
Fit the second segment on the top of the first,
so that when held compressed as described above,
the ring ends point upwards. Position the gap
at 1800 to the first segment gap.
The third segment should be fitted on the top
of the second so that when compressed as describ:d,
the ring ends point downwards. Position the gap
immediately above that of the first segment.
Fit the fourth segment on top of the third so
that when held and compressed, the ring ends
point upwards. Position the gap above that of
the second segment.
When the four laminations are fitted to the
piston check that they are fitted correctly. If
fitted correctly there will appear a circumferential
gap between the bottom two laminations and the
top two laminations as illustrated in fig. J .3.
When fitting ncw rings to original pistons,
clean out piston ring grooves using the old ring
from the appropriate groove for this.
Examine the piston skirt and if there is any
scoring the piston must not he used again.
The piston should be examined carefully for
bruising of the ring grooves and to ensure that the
rings move freely in their grooves.
NOTE. When fitting new rings to wom
cylinder liners, the ring gaps should be checked at
a bore diameter of 4.250 in. (108 mm.).
To Fit Piston and Connecting Rod to Cylinder
Block.
AII connecting rods and caps are plainJy marked
with a number corresponding to their position in
the engine. For method of marking see Fig. J.J.
'[hese numhers are stamped on that side of the
connecting rods and caps which are machined to
take the locating lips of the hearings.
,--J-~-\
~~
C::::::::::--- I
,
I~////~/-
Check rings tor correct gap which must be
within the limits given in Section V.
Fit the rings to the piston in the order shown in
fig. J .2. The gaps of the two compression and
scraper rings must be arranged so that they are
equally spaced around the piston and not in line
with one another.
When fitting achrome plated compression ring.
care should be taken to ensure that it is fitted
correctly. The ring is suitably marked to indicate
how it should be replaced.
When fitting the third laminated compression
ring, care should be taken that the tour lamin-
ations are correctly assem bied to the piston.
To assembie to piston, proceed as follows:-
Examine the laminations and it will be observed
that the tree ends of the ring are not cut square to
the circumference but slope away either to the
right or lelt, depending on which war up the ring
is tumed.
Fit the first segment to the piston 50 that when
held horizontally in the palm of the hand and
radially compressed, the ring ends point down-
wards. Position this ring at the bottom of the
groove with the gap over the gudgeon pin bare.
Fig. J .3. Showing how the laminated compression
ring should be fitted into its groove.
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