12 CYLINDER HEAD ASSEMBLY
Cylinder head
To inspect and to correct12A-12
1Remove the cylinder head assembly, operation
12A-07.
2 Remove the thermostat housing.
3 Inspect the cylinder head for signs of gas or
coolant leakage.
4 Remove the valve springs and the valves,
operation 12A-08.
5 Clean the face of the cylinder head and the
passages for coolant and for lubricating oil. The
water jacket can be cleaned with a special solvent
which must be used in accordance with the
manufacturer's instructions.
6 Test the cylinder head for leaks at the pressure
given in the data and dimensions.
7 When the cylinder head is thoroughly clean,
check it for cracks. Inspect carefully the areas
around the valve seats and around the holes for the
atomiser nozzles.
8 The bottom face of the cylinder head can be
machined if: there is distortion, see paragraph 9;
there are deep scratches; or, for engines without
valve seat inserts, the valve depths are below the
service limit.
9 Use a straight edge and feeler gauges to check
the cylinder head for distortion across and along its
bottom face, see the data and dimensions. If the
distortion is more than the limit given in the data
and dimensions, the bottom face can be machined.
Caution: Remove only the minimum material and
ensure that the thickness of the cylinder head will
not be less than 102,48 mm (4.035 in) after the
cylinder head has been machined.
Notes:
• On AE and YE engines the protrusion of the
atomiser nozzle below the bottom face of the
cylinder head must not be more than 4,82 mm
(0.190 in).
• The nozzle protrusion must be measured with
the nozzle seat washer fitted.
Caution: After the cylinder head has been
machined the valve seats must be corrected to give
the correct valve head depth.Work to the minimum
limit to allow for later wear.
10 Check the valve seats for wear and for damage.
11 Before any work is done on the valve seats,
new valve guides must be fitted, operation 12A-11.
12 Where there is little damage, the valve and
valve seat can be lapped. When the valve seats are
lapped keep the seat as narrow as possible and
ensure that all the compound used to lap the valve
and the seat is removed.
13 More badly damaged valve seats can be
corrected by use of the cutter tool, operation
12A-13, or new inserts can be fitted, operation
12A-14.
12A.20 Perkins Phaser/1000 Series, April 1995
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