Discovery 2. Manual — part 48

ENGINE - V8

OVERHAUL 12-2-65

11. Check the following valve dimensions. Renew

valves as necessary.

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Valve head diameter 'A': Inlet = 39.75 to
40.00 mm (1.56 to 1.57 in).

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Valve head diameter 'A': Exhaust = 34.23 to
34.48 mm (1.35 to 1.36 in).

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Valve stem diameter 'B': Inlet = 8.664 to
8.679 mm (0.341 to 0.342 in).

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Valve stem diameter 'B': Exhaust – 4.0 litre
engines up to engine nos. 55D 05677A; 56D
50787A and 97D 05504A = 8.651 to 8.666
mm (0.340 to 0.341 in).

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Valve stem diameter 'B': Exhaust – 4.0 litre
engines from engine nos. 55D 05678A; 56D
50788A and 97D 05505A and all 4.6 litre
engines = 8.641 to 8.656 mm (0.340 to
0.341 in)

12. Check installed height of valve.

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Valve installed height, end of valve to base
of spring seat, 'C' = 44.163 to 45.288 mm
(1.741 to 1.802 in).

13. Check condition of valve springs. Valve

springs must be replaced as a complete
set.

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Valve spring free length = 48.30 mm (1.90
in).

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Valve spring fitted length = 40.40 mm (1.59
in).

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Spring load - valve closed = 339

±

10 N (76

±

2.25 lbf).

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Spring load - valve open = 736

±

10 N (166

±

2.25 lbf).

14. Check valve stem to guide clearance using the

following procedures:

15. Insert each valve into its respective guide.
16. Extend valve head approximately 13 mm (0.6

in) out of valve seat and position a DTI gauge
to rear of valve head.

17. Move valve towards front of cylinder head and

zero DTI gauge ensuring that stylus of gauge
remains in contact with valve head.

18. Move valve towards rear of cylinder head and

record gauge reading to give valve stem to
guide clearance.

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Valve stem to guide clearance 'D': Inlet =
0.025 to 0.066 mm (0.001 to 0.002 in).

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Valve stem to guide clearance 'D': Exhaust
– 4.0 litre engines up to engine nos. 55D
05677A; 56D 50787A; 97D 05504A = 0.038
to 0.078 mm (0.0015 to 0.003 in).

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Valve stem to guide clearance 'D': Exhaust
– 4.0 litre engines from engine nos. 55D
05678A; 56D 50788A; 97D 05505A and all
4.6 litre engines = 0.048 to 0.088 mm
(0.0019 to 0.0035 in).

19. Renew valve guides as necessary.

20. Using valve guide remover tool LRT-12-037

press valve guide into combustion face side of
cylinder head.

21. Lubricate new valve guide with engine oil and

with tapered portion of guide leading, insert
guide from valve spring side of head.

Note: Service valve guides are 0.025 mm
(0.001 in) oversize on outside diameter to
ensure an interference fit.

22. Fully fit guide using tool LRT-12-039A and

distance piece tool LRT-12-208

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Valve guide installed height 'A' = 15.00 mm
(0.590 in).

23. Ream valve guide to 8.70 mm (0.342 in).

Note: Service valve guides are supplied with an
internal diameter of 8.1 mm 0.025 mm (0.319 in).

24. Position cylinder head stands and mount

cylinder head on stands.

25. Check valve seat insert for pitting, burning,

cracks and wear. Replace as necessary.
Service valve seat inserts are available 0.025
mm (0.001 in) oversize on outside diameter to
ensure interference fit.

ENGINE - V8

12-2-66 OVERHAUL

26. Remove worn valve seat.

CAUTION: Take care not to damage the
counterbore in the cylinder head when
removing valve seats.

27. Heat cylinder head evenly to approximately

120

°

C (250

°

F).

WARNING: Handle the hot cylinder head
with care.

28. Using a suitable mandrel, press new insert fully

into counterbore.

29. Allow cylinder head to air cool.

CAUTION: Renew worn valve guides and/or
valve seats before lapping the valves.

30. Recut valve seat in head and lap in valves

using fine paste.

31. Coat valve with a small quantity of engineer's

blue, insert valve and press into position
several times without rotating. Seating position
should be in centre of valve face.

32. Check valve installed height if valve seats have

been refaced or renewed.

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Valve installed height, end of valve to base
of spring seat, 'A' = 44.16 to 45.29 mm (1.74
to 1.80 in).

33. Reface valves as necessary. If a valve has to

be ground to a knife-edge to obtain a true seat,
renew valve.

34. Cut valve seats using suitable cutters:

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Valve seat angle 'A' = 45

°

.

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Valve seat insert diameter 'B' Inlet = 36.83
mm (1.45 in).

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Valve seat insert diameter 'B' Exhaust =
31.50 mm (1.24 in).

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Seating width 'C' - Inlet = 0.89 to 1.4 mm
(0.035 to 0.055 in).

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Seating width 'C' - Exhaust = 1.32 to 1.83
mm (0.052 to 0.072 in).

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Angle 'D' = 70

°

.

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Angle 'E' = 46

°

to 46

°

25'.

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Angle 'F' = 20

°

.

ENGINE - V8

OVERHAUL 12-2-67

35. Check that cutter blades are adjusted so that

middle of blade contacts area of material to be
cut. Use light pressure and only remove the
minimum of material necessary.

36. Clean valve seat and valve.

Reassembly

1. Clean spring caps, collets and valve springs.
2. Lubricate new valve stem oil seal with clean

engine oil and fit seal.

3. Lubricate valve with clean engine oil and fit

valve.

4. Fit spring and cap, compress spring using tool

LRT-12-034 and fit collets.

5. Release valve spring and remove tool LRT-12-

034.

6. Fit cylinder head gasket.

+

ENGINE - V8, OVERHAUL, Gasket -

cylinder head.

Piston assemblies

$% 12.17.02.01

Disassembly

1. Remove cylinder head.

+

ENGINE - V8, OVERHAUL, Gasket -

cylinder head.

2. Remove oil pick-up strainer.

+

ENGINE - V8, OVERHAUL, Strainer

- oil pick-up.

3. Suitably identify each connecting rod and

piston assembly to its respective cylinder bore.

4. Remove 2 bolts securing each connecting rod

bearing cap.

5. Remove connecting rod bearing cap and

collect connecting rod bearings.

6. Remove ridge of carbon from top of cylinder

bores.

7. Carefully push each piston assembly from the

top of the cylinder.

CAUTION: Ensure that connecting rods do
not contact cylinder bores.

8. Refit bearing cap onto connecting rod, lightly

tighten dowel bolts.

9. Suitably identify each piston to its respective

connecting rod.

ENGINE - V8

12-2-68 OVERHAUL

10. Position body of tool LRT-12-013 in vice.
11. Screw large nut back until flush with end of

centre screw.

12. Push centre screw forward until nut contacts

thrust race.

13. Position remover/replacer LRT-12-126/2 in

LRT-12-013 with its long spigot inside bore of
hexagon body.

14. Locate piston and connecting rod assembly on

centre screw and up to remover/replacer
adapter tool LRT-12-126/2.

CAUTION: Ensure that prongs of remover/
replacer adapter LRT-12-162/2 remain in
contact with piston and do not contact
gudgeon pin.

15. Fit remover/replacer bush LRT-12-126/1 on

centre screw with flanged end facing away from
gudgeon pin.

CAUTION: Ensure that remover/replacer
bush LRT-12-126/1 is correctly located in
gudgeon pin bore of piston.

16. Screw stop nut onto centre screw.
17. Lock the stop nut securely with the lock screw.
18. Push connecting rod to locate end of gudgeon

pin in remover/replacer adapter LRT-12-126/2.

19. Ensure remover/replacer bush LRT-12-126/1

is located in gudgeon pin bore of piston.

20. Screw large nut up to tool LRT-12-013.
21. Hold lock screw and turn large nut until

gudgeon pin is withdrawn from piston.

CAUTION: Ensure that prongs of tool LRT-
12–126/2 remain in contact with piston and
do not contact the gudgeon pin.

22. Dismantle tool LRT-12-013 and remove piston,

connecting rod and gudgeon pin.

Inspect

1. Clean carbon from piston. Inspect piston for

distortion, cracks and burning.

2. Remove piston rings from piston.

3. Measure and record piston diameter at 90

°

to

gudgeon pin axis and 10 mm (0.4 in) from
bottom of the skirt. The piston must be 0.015 to
0.045 mm (0.001 to 0.002 in) smaller than the
cylinder bore.

4. Check gudgeon pin bore in piston for signs of

wear and overheating.

5. Pistons fitted on production are graded 'A' or

'B', the grade letter is stamped on the piston
crown.

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Piston diameter: Grade 'A' = 93.970 to
93.985 mm (3.6996 to 3.7002 in).

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Piston diameter: Grade 'B' = 93.986 to 94.00
mm (3.7002 to 3.7007 in).

6. Worn cylinders fitted with grade 'A' pistons may

be honed to accept the grade 'B' piston
provided that specified cylinder bore and
ovality limits are maintained. Grade 'B'
pistons are supplied as service
replacements. Do not attempt to de-glaze
cylinder bores.

CAUTION: Ensure replacement pistons are
correct for the compression ratio of the
engine. The compression ratio will be found
on the cylinder block adjacent to the engine
serial number.

7. Check gudgeon pins for signs of wear and

overheating.

8. Check clearance of gudgeon pin in piston.

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Gudgeon pin to piston clearance = 0.006 to
0.015 mm (0.0002 to 0.0006 in).