Mitsubishi Lancer Evolution VI. Manual — part 18
ENGINE –
Cylinder Head and Valves
11-47
(6) Make paint marks on the cylinder head bolt heads and
cylinder head.
(7) Give a 90
°
turn to the cylinder head bolts in the specified
tightening sequence.
(8) Give another 90
°
turn to the cylinder head bolts and make
sure that the paint mark on the head of each cylinder
head bolt and that on the cylinder head are on the same
straight line.
Caution
1.
If the bolt is turned less than 90
°
, proper fastening
performance may not be expected. When
tightening the bolt, therefore, be careful to give
a sufficient turn to it.
2.
If the bolt is overtightened, loosen the bolt
completely and then retighten it by repeating the
tightening procedure from step (1).
INSPECTION
CYLINDER HEAD
(1) Check the cylinder head gasket surface for flatness by
using a straightedge and thickness gauge.
Standard value: 0.05 mm
Limit: 0.2 mm
(2) If the service limit is exceeded, correct to meet
specification.
Grinding limit: *0.2 mm
* Includes combined with cylinder block grinding.
Cylinder head height (Specification when new):
131.9 – 132.1 mm
6AE0297
90
°
Paint mark
90
°
9EN0064
ENGINE –
Cylinder Head and Valves
11-48
VALVE
(1) Check the valve face for correct contact. If incorrect, reface
using a valve refacer. Valve seat contact should be
maintained uniform at the center of valve face.
(2) If the margin exceeds the service limit, replace the valve.
Item
Standard value mm
Limit mm
Intake
1.0
0.5
Exhaust
1.5
1.0
(3) Measure valve’s total length. If measurement is less than
specified, replace the valve.
Item
Standard value mm
Limit mm
Intake
109.5
109.0
Exhaust
109.7
109.2
VALVE SPRING
(1) Measure the free height of spring and, if it is smaller
than the limit, replace.
Standard value mm
Limit mm
48.3
47.3
(2) Measure the squareness of the spring and, if the limit
is exceeded, replace.
Standard value
Limit
1.5
°
4
°
VALVE GUIDE
Measure the clearance between the valve guide and valve
stem. If the limit is exceeded, replace the valve guide or
valve, or both.
Item
Standard value mm
Limit mm
Intake
0.02 – 0.05
0.10
Exhaust
0.05 – 0.09
0.15
1EN0264
Free
height
Out of
square
Valve
guide
ENGINE –
Cylinder Head and Valves
11-49
VALVE SEAT
Assemble the valve, then measure the valve stem projection
between the end of the valve stem and the spring seating
surface. If the measurement exceeds the specified limit,
replace the valve seat.
Item
Standard value mm
Limit mm
Intake
49.20
49.70
Exhaust
48.40
48.90
VALVE SEAT RECONDITIONING PROCEDURE
(1) Before correcting the valve seat, check for clearance
between the valve guide and valve and, if necessary,
replace the valve guide.
(2) Using the seat grinder, correct to obtain the specified
seat width and angle.
(3) After correcting the valve seat, lap the valve and valve
seat using lapping compound. Then, check the valve
stem projection (refer to VALVE SEAT in INSPECTION).
VALVE SEAT REPLACEMENT PROCEDURE
(1) Cut the valve seat to be replaced from the inside to thin
the wall thickness. Then, remove the valve seat.
(2) Rebore the valve seat hole in the cylinder head to a
selected oversize valve seat diameter.
Valve seat ring hole diameter
Item
Standard value mm
Intake
0.30 O.S.
35.30 – 35.33
0.60 O.S.
35.60 – 35.63
Exhaust
0.30 O.S.
33.30 – 33.33
0.60 O.S.
33.60 – 33.63
(3) Before fitting the valve seat, either heat the cylinder head
up to approximately 250
°
C or cool the valve seat in liquid
nitrogen, to prevent the cylinder head bore from galling.
(4) Using a valve seat cutter, correct the valve seat to the
specified width and angle.
See “VALVE SEAT RECONDITIONING PROCEDURE”.
DEN0212
Valve stem end
Valve stem
projection
Spring seating
surface
6EN0491
0.9 – 1.3 mm
43.5
°
– 44
°
0.5 – 1 mm
0.5 – 1 mm
1EN0275
Height of
seat ring
Oversize I.D.
ENGINE –
Cylinder Head and Valves
11-50
VALVE GUIDE REPLACEMENT PROCEDURE
(1) Force the valve guide out toward the cylinder block using
a press.
(2) Machine the valve guide hole in the cylinder head to
the size of the oversize valve guide to be installed.
Caution
Do not use the valve guide of the same size as the
removed one.
Valve gauge hole diameters in cylinder head
Item
Standard value mm
0.05 O.S.
12.05 – 12.07
0.25 O.S.
12.25 – 12.27
0.50 O.S.
12.50 – 12.52
(3) Press-fit the valve guide until it protrude specified value
19.5 mm as shown in the illustration.
Caution
1.
Press the valve guide from the cylinder head top
surface.
2.
Valve guide for intake valve and that for exhaust
valve are different in length. (45.5 mm for intake
valve; 50.5 mm for exhaust valve)
(4) After the valve guide has been installed, insert a new
valve to check for smooth sliding motion.
1EN0106
Protrusion
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