II
.-
-
-
•
--
. -
.......
,
...
,.
li~
I
·(O'O~rl05
mm)
'
331'5
Group
21
Reconditioning engine
Cylinder head, cfeaning - inspection
Grind-in valves
with
paste
Clean valves
thoroughly
after
grinding
.
Replacing vafve seats
Operations F13-21
F12
Valve
guides
must
be replaced
before
replacing
seats,
see
F6-8.
page
47.
F13
Clean
combustion
chamber
Edge
of
seat must be clearly visible af
ter
cleaning.
F14
Remove valve
seat
Mill valve seat, using cutters such
as
Mira
(pIN
9986045). Refer to manufacturer's instructions. Make
sure that seat in
cylinder
head is
not
damaged.
Clean surfaces thoroughly.
F15
Measure
diameter
of
seat
recess
in cylinder
head
and
of valve
5eat
Use
an
internai
micrometer
to measure seat recess.
Standard
(production version)
Diameter, seat recess,
mm
(in)
intake
.................
37.000-37.016
(1.4567-1.4573)
exhaust ..............
33.000-33.016
(1.2992-1.299B)
Diameter, seat,
intake .................
37.090-37.105
(1.4602-1.460B)
exhaust ..............
33.090-33.105
fl.3028-1.3033)
Oversize
(replacement parts version)
Diameter, seat recess,
mm
(in)
intake .................
37.200-37.216
(1.4646-1.4652)
exhaust ..............
33.200-33.216
(
1.3071-1.3
077)
Diameter, seat.
intake .................
37.290-37.305
11.4681-1.46B7)
exhaust ..............
33.290-33.305
(
1.3106-1.3112)
When replacing valve seats: the interference between
the
valve seat and its bore in the cylinder head shall be
0.074-0.105
mm
(0.0029-0.0041 in) i.e. valve seat
diameter must be
0.074-0.105
mm
(0.0029-0.0041 in)
greater than the
diameter
of
the bore in the cylinder
head. Replace
cylinder head
if
interference
is
too
smal
l.
Mill
seat recess
if
interference is
too
large.
49
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