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36
FIAT. 850 PASSENGER CARS
Main Specifications. Pistons· Pins· Rings - Connecting Rods - Bearings (contInued).
DESCRIPTION
in
I
mm
- -
1
- -
--
Piston pin
in
boss:
-
clearance of new parts
.
·
.0003 to .0006
0.008 to 0.016
- wear limit
·
·
.0020
0.05
Piston ring side fit (vertically):
- first compression
lclearance of new parts
.0018 to .0030
0.045 to 0.017
ring.
wear limit
. . . . .
.008
0.15
second oil
ring
~c1earance
of new parts
.0010 to .0022
0.025 to 0.057
-
wear limit
. . . . .
.006
0.15
-
third radial-slotted
Jclearance of new parts
.0011 to .0030
0.027 to 0.017
oil ring
wear
limit
. . . . .
.008
0.15
Ring end gap
in
bore:
- first compression ring: clearance of new parts
.0079 to .0138
0.20 to 0.35
- second oil ring: clearance of new parts
.0079 to .0138
0.20 to 0.35
- third radial-slotted oil ring (compressed)
touch
fit
Piston rings for service:
-
compression and oil rings
·
Std, .0079-.0157-.02360.5.
0.2-0.4-0.6
- radial-slotted oil ring
·
Std,
.0157 0.5.
004
Connecting rod big end bore
.
·
1.7188 to 1.7193
43.657 to 43.670
--
Connecting rod small end bore .
.7850 to .7856
19.943 to 19.954
Standard con rod bearing shell thickness
.0711 to .0713
1.807 to 1.813
Connecting rod bearings for service
Std, .01-.02-.03-.04 U.S.
0.254-0.508-0.762-1.01
e
- - -
Piston pin-to-small end press fit .
·
. ·
.0006 to .0015
0.QI6 to 0.039
- - -
Connecting rod bearing-to-joumal:
-
clearance of new parts
.0010 to .0028
0.026 to 0.071
- wear limit
.004
0.10
Cleaning.
Remove carbon deposits from piston top and
ring grooves using a curved scraper tool.
Eliminate all foreign matter from oil holes in
piston and connecting rod.
Rings are cleaned with extremely refined emery
cloth.
Next to cleaning, painstakingly check parts for
cracks or such damages as replacement is required.
Checking Piston Clearance in Bore and
Piston Pin Clearance in Boss.
Clearance of pistons in cylinder bores should
be checked
(fig.
40)
having
mind to their class
division.
Therefore pistons and cylinders should
belong to the same class.
Standard pistons are also graded into three
divisions according to the pin boss bore.
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