Infiniti QX4 (R50). Manual — part 420
CAUTION:
I
When installing camshafts, chain tensioners, oil seals, or
other sliding parts, lubricate contacting surfaces with new
engine oil.
I
Apply new engine oil to threads and seat surfaces when
installing cylinder head, camshaft sprocket, crankshaft
pulley, and camshaft bracket.
I
Attach tags to valve lifters so as not to mix them up.
Removal
NBEM0017
1.
Remove engine from vehicle. Refer to EM-57, “Removal and
Installation”.
2.
Remove exhaust manifolds in reverse order of installation.
Refer to EM-13, “Exhaust Manifold”.
3.
Place engine on a work stand.
4.
Remove aluminum oil pan. Refer to EM-15, “Removal”.
5.
Remove timing chain. Refer to EM-23, “Removal”.
SEM964F
6.
Remove intake manifold in reverse order of installation. Refer
to “TIGHTENING PROCEDURES”, EM-12.
7.
Remove water outlet.
SEM442G
8.
Remove rear timing chain case bolts.
I
Loosen in numerical order as shown in the figure.
SEM168FA
9.
Remove rear timing chain case.
GI
MA
LC
EC
FE
AT
TF
PD
AX
SU
BR
ST
RS
BT
HA
SC
EL
IDX
CYLINDER HEAD
Components (Cont’d)
EM-39
SEM447G
10. Remove O-rings to cylinder head.
SEM534G
11. Remove O-rings to cylinder block.
SEM443G
12. Remove CVTC valves.
SEM856E
SEM857E
13. Remove intake and exhaust camshafts and camshaft brackets.
I
Equally loosen camshaft bracket bolts in several steps in the
numerical order shown in the figure.
For reinstallation, be sure to put marks on camshaft
bracket before removal.
CYLINDER HEAD
Removal (Cont’d)
EM-40
SEM444G
14. Remove RH and LH camshaft chain tensioners from cylinder
head.
SEM859E
SEM860E
15. Remove cylinder head bolts.
I
Cylinder head bolts should be loosened in two or three
steps.
I
A warped or cracked cylinder head could result from
removing in incorrect order.
SEM863E
16. Remove cylinder head.
Disassembly
NBEM0043
Remove valve component parts.
Refer to EM-35, “VALVE OIL SEAL”.
I
Check the clearance before removing the valve guide. Refer to
EM-43, “VALVE GUIDE CLEARANCE”.
GI
MA
LC
EC
FE
AT
TF
PD
AX
SU
BR
ST
RS
BT
HA
SC
EL
IDX
CYLINDER HEAD
Removal (Cont’d)
EM-41
SEM861E
Inspection
NBEM0019
CYLINDER HEAD DISTORTION
NBEM0019S01
Clean surface of cylinder head.
Use a reliable straightedge and feeler gauge to check the flatness
of cylinder head surface.
Check along six positions shown in the figure.
Head surface flatness: Limit 0.1 mm (0.004 in)
If beyond the specified limit, resurface or replace it.
The limit for cylinder head resurfacing is determined by the
cylinder block resurfacing.
Resurfacing limit:
Amount of cylinder head resurfacing is “A”.
Amount of cylinder block resurfacing is “B”.
The maximum limit : A + B = 0.2 mm (0.008 in)
After resurfacing cylinder head, check that camshaft rotates freely
by hand. If resistance is felt, cylinder head must be replaced.
Nominal cylinder head height:
126.3 - 126.5 mm (4.972 - 4.980 in)
SEM191F
CAMSHAFT VISUAL CHECK
NBEM0019S02
Check camshaft for scratches, seizure and wear.
CAMSHAFT RUNOUT
NBEM0019S03
1.
Measure camshaft runout at A and B as shown in the figure.
Runout (Total indicator reading):
Limit 0.05 mm (0.0020 in)
2.
If it exceeds the limit, replace camshaft.
SEM549A
CAMSHAFT CAM HEIGHT
NBEM0019S04
1.
Measure camshaft cam height.
Standard cam height:
Intake and exhaust
44.465 - 44.655 mm (1.7506 - 1.7581 in)
Cam wear limit:
0.2 mm (0.008 in)
2.
If wear is beyond the limit, replace camshaft.
SEM862E
CAMSHAFT JOURNAL CLEARANCE
NBEM0019S05
1.
Install camshaft bracket and tighten bolts to the specified
torque.
2.
Measure inner diameter “A” of camshaft bearing.
Standard inner diameter:
No. 1: 26.000 - 26.021 mm (1.0236 - 1.0244 in)
No. 2, 3, 4: 23.500 - 23.521 mm (0.9252 - 0.9260 in)
CYLINDER HEAD
Inspection
EM-42
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