BMW 5251 Service Manual page 235

Cylinder Head and valvetrain1
Valve seats
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The valve seats should be resurfaced whenever new valves
or valve guides are installed. Cutters are required to resur-
face the seats. Always check the valves for leaks after recon-
ditioning a valve seat as described above. Table e. Valve
seat specifications lists valve seat dimensions.
Table e. Valve seat specifications (refer to figure)
All
6
cylinder All
8
cylinder
engines (1997- engines (1997-
Specification 2002) 2002)
B l l l l o c
A
-Valve seat angle
45"
--.
--
45"
B
-
Correction angle,
15" 15"
outside
C
-
Correction angle, 60"
inside
D -Valve seat width
intalte 1.65 i0.25 rnrn 1.25 +0.25 rnm
(0.065 c0.010 in) (0.049 f 0.010 in)
exhaust 1.65 c0.25 rnm
1.65 i0.35 rnm
(0.065 fO.O1O in) (0.065 c0.014 in)
E -
Valve seat outside diameter
intake 32.4 mm (1.276 in) 34.5 mm (1.358 in)
exhaust M52: 29.4 rnm 30.0 rnm (1.181 in)
(1.157 in)
-
M52 TU,
M54: 30.0 mrn
(1.181 in)
NOTE-
Standard size replacement valve seats are not available from
BMW Replacement valve seats are only available from BMW
in 0.4 mm oversize (oversized in both height and diameter).
The manufacturer does not provide specifications for valve
seat replacement for the engines covered by this manual.