Porsche 928 Workshop Manual page 231

15
Engine I Cylinder Head, Valves 926
Machining cylinder-head mating face (32~valve engines)
Checking the cylinder head for dlstortion
Check the sealing surface of the cylinder
head for distortion using a feeler gauge
straightedge.
Distortion limit of mating surface: 0.05 mm
Cylinder heads with distorted mating faces
can be remachined and reused. Admissible
distortion after machining: 0.03 mm.
Machining cylinder heads
As a rule, both cylinder heads must be ma-
chined by the same amount to ensure correct
seating of the regulator housing.
Machine sealing surface of the cylinder head
only until a straight surface is obtained.
Max. wear limit: 146.6 mm.
Note for machining of the sealing surface:
Max. roughness = 0.015 mm
If machining causes the actual value to be
below the tolerance applicable to new parts,
use a 1.4 mm thick cylinder head gasket
(available from the parts service) when fitting
the cylinder head.
New-part size A = 147 5 0.1 mm
Wear limit A = 146.6 mm
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15-1125 Machining cylinder-head mating face (32~valve englnes)
Printed in Germany - XXVII, 1991