Porsche 928 Workshop Manual page 227

15 Engine/Cylinder Head, Valves
928
REPLACING VALVE GUIDES
l.Clean cylinder head and check.
If the valve seats or mating
faces of the cylinder heads
cannot be remachined, the
cylinder heads are not suitable
for replacement valve guides.
2.Position cylinder head on
press-out base.
3.Working from the camshaft side to
the combustion-chamber side,
press out valve guides with a
press.
4.Use internal calipers to measure
bores in cylinder head.
5.Machine KD valve guide, part no.
944 104 327 51 (external diameter
11.26 mm) to correct size.
Loading must be 0.06 - 0.08 mm
for both intake and exhaust valve
guides.
Example:
Bore in cylinder head measured
11.020 mm. Machine outside diameter
of KD valve guide to
11.080 or
11.10 mm.
Replacing valve guides, ENGINE TYPE
M 28. 41/42,
187 MODELS ONWARD
It is essential to place a
1
mm
thick washer on the cylinder-head
mating face
before
installing the
valve guide.
6.Heat cylinder head to 170°C. Coat
valve guides with talcum powder,
tap lightly into position, align
and, using a thrust piece and
working from the camshaft side,
press into cylinder head until
seated.
Caution:
Do not maintain the temperature of
170°C for more than a maximum of 90
minutes.
l
a
15 - 112 h
Replacing Valve Guides
Printed in Germany