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34
FIAT· 850 PASSENGER CARS
Fig. 38 -. Reaming tappet seats on crankcase.
1. Reamer handle. - 2. Tappet seat reamer A. 90318/1.
Check the wear of internal faces of bushings as
well as the clearance of bushings to camshaft jour-
nals against specifications on page 29.
Checking and Reaming Tappet Seats.
Should excessive play (over .0031"·0.08 mrn)
between tappets and their seats on crankcase be
detected, replace tappets
by
oversizes_ Gauge the
diameter of the tappet seat in order to determine
the amoWlt of wear and consequently the width
of reaming necessary.
Tappets come for service
in two oversizes:
.002" and
.004"
(0.05 and
0.10 mrn).
Use reamer A. 90318/1 if .002" (0.05 mrn) oversize
tappets must be fitted, while reamer A. 90318/2
will ream seat for .004" (0.10 nun) oversize tappets
(fig. 38).
Next check that clearance between tappets and
seats
is
as recommended, or .0004" to .0018"
(0.010 to 0.046 mrn).
For more data on tappets, see covering chapter,
page
65.
Q
0
0
D"cl7
0
11
0
0
/ 0 0
of
\
l/
i' = '
o©
1'-
j-~
«)
a
~
0 0 0
0
0 =0 0;::: Oi)
0
- - J
r
~
' -
0
1 -
-
0 --
HO
-
V
~
cf:
v
~/';
" I
0
15'107/
15UO~~
I-
1
5UO
;
1
5'110
5Ul0
5'110
b-
r
0
0
0
I - -
~
0
65.000
_I
0
65,050
0
0
0
0
0
0
~
UU
Fig. 39.
Critical dimensions of crankcase (metric).
Diameter of main bearing saddle bores and cyJJnder
bores.
• Cylinder bores are graded Into classes with
.0004" (0.01 mm) progression.
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