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Mitsubishi 380. Manual - part 452

CYLINDER HEAD AND VALVES

ENGINE OVERHAUL <3.8L ENGINE>

11B-34

INSPECTION

M1113007000464

CYLINDER HEAD

1. Check the cylinder head gasket surface for flatness by using

a straightedge in the directions of A through G shown in the
illustration.

Standard value: 0.03 mm (0.0012 inch)
Limit: 0.2 mm (0.007 inch)

2. If the service limit is exceeded, correct to meet the

specification.

Grinding limit: *0.2 mm (0.007 inch)

3. *If the service limit is exceeded, correct to meet the

specification.

Cylinder head height (specification when new):

120 mm (4.7 inches)

VALVE

1. Check the valve face for correct contact. If incorrect, reface

using a valve refacer. The valve should make a uniform
contact with the seat at the center of the valve face.

2. If the margin exceeds the service minimum limit, replace the

valve.

Standard value:

<Intake> 1.0 mm (0.04 inch)
<Exhaust> 1.2 mm (0.05 inch)

Minimum limit:

<Intake> 0.5 mm (0.02 inch)
<Exhaust> 0.7 mm (0.03 inch)

3. Measure the valve's total length. If the measurement is less

than specified, replace the valve.

Standard value:

<Intake> 110.30 mm (4.343 inches)
<Exhaust> 112.11 mm (4.414 inches)

Minimum limit:

<Intake> 109.80 mm (4.323 inches)
<Exhaust> 111.61 mm (4.394 inches)

AKX00733

AKX00619

MARGIN

VALVE SEAT

CONTACT

AKX00624

CYLINDER HEAD AND VALVES

ENGINE OVERHAUL <3.8L ENGINE>

11B-35

VALVE SPRINGS

1. Measure the free height of the spring and, if it is smaller than

the minimum limit, replace the spring.

Standard value: 50.6 mm
Minimum limit: 49.6 mm

2. Measure the squareness of the spring and, if the limit is

exceeded, replace the spring.

Standard value: 2

° or less

Limit: 4

VALVE GUIDES

Measure the clearance between the valve guide and valve
stem. If the limit is exceeded, replace the valve guide, valve, or
both.

Standard value:

<Intake> 0.02

− 0.05 mm (0.0008 − 0.0019 inch)

<Exhaust> 0.04

− 0.06 mm (0.0016 − 0.0023 inch)

Limit:

<Intake> 0.10 mm (0.003 inch)
<Exhaust> 0.15 mm (0.005 inch)

VALVE SEAT

Assemble the valve, then measure the valve stem projection
between the end of the valve stem and the spring seating sur-
face. If the measurement exceeds the specified limit, replace
the valve seat.

Standard value:

<Intake> 48.30 mm (1.902 inches)
<Exhaust> 51.71 mm (2.036 inches)

Limit:

<Intake> 48.80 mm (1.921 inches)
<Exhaust> 52.21 mm (2.056 inches)

VALVE SEAT RECONDITIONING PROCEDURE

CAUTION

Before correcting the valve seat, check the clearance
between the valve guide and valve and, if necessary,
replace the valve guide.
1. Using the special tool or a seat grinder, correct to obtain the

specified seat width and angle.

2. After correcting the valve seat, lap the valve and valve seat

using lapping compound. Then, check the valve stem
projection.

AKX00607

2˚

FREE

HEIGHT

AKX00714

VALVE

GUIDE

STEM OUTSIDE

DIAMETER

GUIDE INSIDE DIAMETER

AKX00695

SPRING SEATING

SURFACE

VALVE STEM END

VALVE STEM

PROJECTION

AK101830AB

0.9 – 1.3 mm

(0.04 – 0.05 in)

65˚

15˚

25˚

43.5˚ – 44˚

0.9 – 1.3 mm

(0.04 – 0.05 in)

CYLINDER HEAD AND VALVES

ENGINE OVERHAUL <3.8L ENGINE>

11B-36

VALVE SEAT REPLACEMENT PROCEDURE

CAUTION

Before replacing the valve seat, check the valve guide and,
if necessary, replace the valve guide.
1. Cut the valve seat 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.

Seat ring hole diameter:

Intake valve

0.3 oversize 37.80

− 37.83 mm (1.4882 − 1.4894

inches)
0.6 oversize 38.10

− 38.13 mm (1.5000 − 1.5012

inches)

Exhaust valve

0.3 oversize 34.80

− 34.83 mm (1.3701 − 1.3713

inches)
0.6 oversize 35.10

− 35.13 mm (1.3819 − 1.3831

inches)

3. Before fitting the valve seat, either heat the cylinder head up

to approximately 250

°C (482°F) 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. Using a valve seat cutter, correct
the valve seat to the specified width and angle. See "VALVE
SEAT RECONDITIONING PROCEDURE" on the previous
page.

VALVE GUIDE REPLACEMENT PROCEDURE

1. Remove the snap ring from the exhaust valve guide.

2. Using a press, remove the valve guide toward the cylinder

head gasket surface.

CAUTION

Do not install a valve guide of the same size again.

3. Re-bore the valve guide hole of the cylinder head so that it

fits the press-fitted oversize valve guide.

Valve guide hole diameter:

0.05 oversize 11.05

− 11.07 mm (0.4350 − 0.4358 inch)

0.25 oversize 11.25

− 11.27 mm (0.4429 − 0.4437 inch)

0.50 oversize 11.50

− 11.52 mm (0.4528 − 0.4535 inch)

4. Install the new snap ring into the groove of exhaust valve

guide.

AKX00610

0.5 – 1 mm

(0.020 – 0.039 in)

0.5 – 1 mm (0.020 – 0.039 in)

CUT

AWAY

AKX00611

HEIGHT OF

SEAT RING

OVERSIZE DIAMETER

AKX00712

REMOVAL

INSTALLATION

PRESS

PUSH ROD

VALVE
GUIDE

OIL PAN AND OIL PUMP

ENGINE OVERHAUL <3.8L ENGINE>

11B-37

5. Press-fit the valve guide until it protrudes 14 mm (0.55 inch)

from the cylinder head top surface as shown in the
illustration.

NOTE: When press-fitting the valve guide, work from the cylin-
der head top surface.

NOTE: After installing the valve guides, insert new valves in
them to check for sliding condition.

OIL PAN AND OIL PUMP

REMOVAL AND INSTALLATION

M1113008100420

AKX00727

14 mm

(0.55 in)

AK302971

14 ± 1 N·m

122 ± 9 in-lb

10 ± 2 N·m

87 ± 17 in-lb

19 ± 3 N·m

14 ± 2 ft-lb

11 ± 1 N·m

95 ± 9 in-lb

39 ± 5 N·m

29 ± 4 ft-lb

9.0 ± 3.0 N·m

80 ± 26 in-lb

10.8 ± 0.9 N·m

96 ± 7 in-lb

9.0 ± 3.0 N·m

80 ± 26 in-lb

9.0 ± 2.0 N·m

80 ± 17 in-lb

44 ± 5 N·m

33 ± 4 ft-lb

23 ± 3 N·m

18 ± 2 ft-lb

10 ± 2 N·m

87 ± 17 in-lb

41 ± 8 N·m

30 ± 6 ft-lb

14 ± 2 N·m

122 ± 17 in-lb

11 ± 1 N·m

95 ± 9 in-lb

APPLY ENGINE OIL

TO ALL MOVING

PARTS BEFORE

INSTALLATION.

Content .. 450 451 452 453 ..