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