Content .. 27 28 29 30 ..

Defender 90 / 110 / 130. Manual - part 29

2.25

LITRE PETROL AND DIESEL CYLINDER HEAD

. . .

EXAMINATION OF COMPONENTS

Petrol engine

32. Examine

t h e

cylinder head

cracks and

distortion. Burnt, pitted and pocketed seats must
be repaired.

Diesel engine

33. Same as for petrol engine and in addition, worn or

damaged exhaust seat inserts should be renewed,
as described later.

Hot

and

injector shrouds

examine and

renew

When carrying

out normal top overhaul work on the

cylinder head

i t

is not necessary to

either the

injector shrouds o r

hot plugs.

Small surface cracks

in the hot plug, extending from the

opening to approximately

i n )

length

can be ignored. However any severe

appear on

the face

of the hot plug, before attempting to remove

i t ,

closely inspect t h e cylinder head for

signs

of cracks,

particularly  between  the  inlet  and  exhaust  valve  seats.
Such cracking indicates that  the engine has overheated,
usually  through  lack  o f   coolant,  and  the  cylinder  head

scrapped.

. .

34.

To remove a hot plug, insert

a thin soft metal drift

through the injector shroud throat and tap the

hot

plug from the inside. Once removed a faulty hot
plug cannot be restored and must be renewed.

35. I f the injector shroud is damaged, drift the shroud

out towards the injector bore.

36. Thoroughly clean out the combustion chamber.

The

hole in the side of the injector shroud is for

manufacturing purposes only but at the same
can be used as a guide when refitting the shroud.

37. Smear a little oil on t h e shroud and insert into the

cylinder head with the

hole pointing towards the

centre

of t h e cylinder head, and drift into

position.

38. Fit the hot plugs by tapping

with

mallet, and locate with a new roll pin.

hot

plugs are loose

in the cylinder head they may be

retained

with

a little grease.

39.

fitted,

hot plugs must be checked with

dial test indicator to ensure that they

not

protrude above the level

of the cylinder head Cace

more than

0,025

(0.001

in) and are not

recessed below the level of the cylinder head face
more than

i n ) .

2.25 LITRE PETROL AND DIESEL CYLINDER HEAD

Petrol and diesel engines

40. Chcck the valve guides for wear by inserting a

new valve

in the appropriate guide

above

the seat. If movement across the head exceeds

(0.006 in) renew the guide.

41. Inspect the valves and discard any that are burnt,

bent

or distorted. Check the stems for wear by

inserting in a new guide. If wear is
discard the valve. Valve faces that are pitted o r
ridged but otherwise serviceable may be refaced.

42. Renew push rods that are bent

or have worn

scored ball

or socket ends.

Renew

push rod

tube seals (Diesel only)

43. Whilst this is rarely necessary the procedure is

44. Drive out the old push rod tubes using a suitable

nevertheless as follows.

drift.

NOTE: Later engines are fitted with tubes without seals.
See 2.5 litre Diesel engine

for renewal.

45. Fit new sealing rings to new push rod tubes and

smear with silicone MS4 grease.

46. Insert the new tubes, chamfered end first from

t h e

combustion  chamber  side.  Align  t h e   flat  on  the
push  rod  tube at right  angles to an  imaginary  line
between  the  centre

of the push rod tube and

centre of the hot plug.

47. Press the push

rod tubes into position whilst

maintaining the alignment.

Also ensure that the

chamfers

on the tubes and in the cylinder head are

fully engaged.

Renew valve guide

48. Support the cylinder head, combustion chamber

uppermost on pieces of timber of sufficient
thickness

to allow clearance

for the valve guides

to be driven out.

Using special drift 274400

for inlet guides and

274401 for exhaust

or suitable alternatives

drive

out the old guides from the combustion face

side.

NOTE: The illustration shows

a petrol engine

cylinder head.

. .

2.25

LITRE PETROL AND DIESEL CYLINDER HEAD

.,.

I .

50.

Turn

the cylinder head over

so the combustion

chambers face downwards. Since the

inlet and

exhaust valve guides are dimensionally different it
is important that the correct guides are fitted to

the appropriate ports.

51.

Lubricate new guides with engine

oil and using

special drift 600959 for the exhaust and 601508 for
the

valve guides

or suitable alternatives,

drive

new guides until the shoulder

flush

with the casting.

53. The special set of hand tools recommended

for

refacing include expandable pilots that fit tightly
into new

or worn guides to ensure that the valve

seat is concentric with valve guide.

The refacing

tool has tungsten carbide cutters and can be used
to cut

a seat in a new exhaust seat insert.

54. Select the correct expandable collet for the valve

guide concerned

i.e.

for inlet guides and

for exhaust.

55.

Loosely assemble the collet, expander and nuts.

Ensure that the chamfered end of the expander is
towards the collet.

Reface cylinder head valve seats

52. Damaged or worn valve seats can be refaced

provided they are not abnormally wide due to
repeated refacing operations.

instruction 64.

56. Insert the assembled pilot into the valve guide

from the combustion face side of the cylinder

head until the shoulder contacts

valve

and the whole of the collet is inside the valve

guide.

57. Expand the collet in the guide by turning the

bar clockwise whilst holding

knurled

nut.

58.

Select t h e appropriate angled cutter for the seats
to be cut.

continued

Correctly seated valve

Undesirable condition

C. Method

of rectification

2.25 LITRE PETROL AND DIESEL CYLINDER HEAD

NOTE: MS 621 is a 45" and 15" cutter and MS 627
is 30" only.

- Petrol engine

inlet valve seat 30"

Diesel engine

inlet

valve seat

45"

exhaust valve seat 45"

See illustrations following instruction

68.

59. Ensure that the cutter blades are correctly fitted

to the

head with the angled end

of the blade

downwards facing the work, as illustrated. Check
that the cutter blades are adjusted so that the
middle

the blade contacts the

of material

to be cut. Use the key provided

i n the hand set

MS 76.

60.

Fit the wrench to the cutter head and turn

clockwise using only very light pressure. Continue
cutting to approximately the centre of the existing
seat.

61. T o check. the effectiveness of

cutting

operation use engineers' blue or a feeler gauge
made from cellophane.

62. Smear a

quantity

of engineers' blue round

the valve seat and revolve

a properly ground valve

.....

against the seat.

continuous

fine line should

appear round the valve.

there is a gap

of not

more than 12

i t

can be corrected by lapping.

63. Alternatively, insert a strip ofcellophanc between

the valve and seat, hold the valve down by the
stem and slowly pull out

t h e

cellophane.

If there is

a drag the seal is satisfactory

in that spot. Repeat

this

at least eight places. Lapping-in

will

correct

a small open spot.

64. After several trueing-up o r

operations

valve seats may  have an excessive width  which can
be reduced  by  obtaining special  correction cutters
which narrow t h e  seat by  removing metal from the
top  and  bottom  of  the  scat.

60" cutter is

recommended for bottom narrowing and

for

top

narrowing use a

cutter

(MS 621) for a 30" valve

seat and a 30" cutter for a 45" seat. The

correction cutters as

for refacing cutters.

very

light  pressure  removing  only  the
material  necessary.  Once  the  seats  have  been
reduced  carry  out  the  normal  refacing  operation

as previously described.

of assembly and operation is used for-

Renew

exhaust seat

inserts

(Diesel only)

65. Hold the cylinder head

in a vice, wear

protective goggles and grind the old insert

until

thin

enough

be cracked and prised out.

Take care not to damage

insert pocket.

66. Remove any burrs and swarf from the pocket.

Failure to do this could cause the new insert to
crack when being fitted.

67. Assemble the new insert to the replacer tool

number 530625

so that the chamfered edge

the

insert is

Using

suitable bolt and

n u t

draw

insert into the cylinder head pocket.

Cut new

seat using cutter

MS 621.

Content .. 27 28 29 30 ..