Porsche 928 Workshop Manual page 229

15
Engine I Cylinder Head, Valves
928
Machining cylinder-head mating face (32-valve
engines)
Checking the cylinder head for distortion
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 ? 0.1 mm
Wear limit A = 146.6 mm
1126-15
Cylinder head refacing dimensions and
identification
New dimension : 147* 0.1 mm
Gasket : 1.1 mm
Identification
: none
Refacing dimension
: 146.8 to 146.6 mm
Gasket
: 1.4 mm
Identification :N
Identlflcatlon: "N"
Engrave on exhaust side between cylinder 2
and 3 as well as 6 and 7, respectively, on the
casting lug below the cylinder head cover
sealing surface.
Height of "N" character: 6 mm
15- 1121
Machining cylinder-head matlng face (32~valve englnes)
Printed
in
Germany
-
XXIX, 1992