Isuzu N-Series. Service manual — part 319
6A-18 ENGINE MECHANICAL
Camshaft and Camshaft Bearing Clearance
Use an inside dial indicator to measure the camshaft
bearing inside diameter.
If the clearance between the camshaft bearing inside di-
ameter and the journal exceeds the specified limit, the
camshaft bearing must be replaced.
Reassembly
1. Key
2. Camshaft Gear
• With the projection of the camshaft gear center
boss turned to the camshaft side, set it to the knock
pin and install the camshaft gear.
Tighten:
Camshaft gear bolt to 142 N
⋅m (14.5 kg⋅m / 105 lb⋅ft)
3. Camshaft Bearing Lower
4. Camshaft Assembly
5. Camshaft Bearing Upper
6. Camshaft Bearing Cap
7. Valve Cap
8. Rocker Arm Shaft Assembly
Above works refer to “CYLINDER HEAD” section
in this manual.
Camshaft Bearing Inside
Diameter
mm (in)
Standard
40.000 — 40.037
(1.5748 — 1.5763)
Camshaft Bearing Clear-
ance
mm (in)
Standard
Limit
0.025 — 0.087 (0.00098
— 0.00343)
0.15 (0.0059)
N6A0147E
N6A0148E
N6A0149E
ENGINE MECHANICAL 6A-19
ROCKER ARM ASSEMBLY
Component
Disassembly
1. Rocker Arm Shaft Assembly
1) Loosen the rocker arm shaft bracket nuts and
bolts in numerical order a little at a time and re-
move the rocker arm shaft assembly with the
camshaft brackets.
2) Leave the (1) indicated bolt unremoved on this
occasion, since it is the rocker arm fixing bolt.
Caution:
Failure to loosen the rocker arm shaft bracket nuts and
bolts in numerical order a little at a time will adversely af-
fect the rocker arm shaft.
2. Valve Cap
Caution:
Take sufficient care not to let the valve caps fall into the
gear case or oil return hole.
3. Camshaft Bracket
4. Rocker Arm
5. Spring
6. Rocker Arm Bracket
7. Camshaft Bracket
Legend
1. Rocker arm shaft assembly
5. Spring
2. Valve cap
6. Rocker arm bracket
3. Camshaft bracket
7. Camshaft bracket
4. Rocker arm
8. Rocker arm shaft
N6A0150E
N6A0150E
6A-20 ENGINE MECHANICAL
8. Rocker Arm Shaft
Inspection and Repair
Make the necessary adjustments, repairs, and part re-
placements if excessive wear or damage is discovered
during inspection.
Rocker Arm Shaft Run-Out
1) Place the rocker arm shaft on V-blocks.
2) Use a dial indicator to measure the rocker arm
shaft central portion run-out.
If the run-out is very slight, correct the rocker
arm shaft run-out with a bench press. The rock-
er arm must be at cold condition.
If the measured rocker arm shaft run-out ex-
ceeds the specified limit, the rocker arm shaft
must be replaced.
Rocker Arm Shaft Outside Diameter
Use a micrometer to measure the rocker arm fitting por-
tion outside diameter.
If the measured value is less than the specified limit, the
rocker arm shaft must be replaced.
Rocker Arm Bushing Inside Diameter
Use either a vernier caliper or a dial indicator to measure
the rocker arm bushing inside diameter.
Check to see if the rocker arm oil port is free of obstruc-
tions.
Rocker Arm Shaft Run-Out
mm (in)
Limit
0.3 (0.012)
Rocker Arm Shaft Out-
side Diameter
mm (in)
Standard
Limit
21.979 — 22.000
(0.8653 — 0.8661)
21.85 (0.8602)
N6A0152E
Rocker Arm Bushing
Inside Diameter
mm (in)
Standard
Limit
22.010 — 22.035
(0.8665 — 0.8675)
22.15 (0.8720)
Rocker Arm and Rocker
Arm Shaft Clearance
mm (in)
Standard
Limit
0.010 — 0.056 (0.0004
— 0.0022)
0.2 (0.0079)
N6A0153E
N6A0154E
ENGINE MECHANICAL 6A-21
If necessary, use compressed air to clean the rocker
arm oil port.
Rocker Arm Roller and Rocker Arm Pin
1. Pass a string through the rocker arm-roller clear-
ance and measure the roller protrusion while pull-
ing both ends of the string in the arrow-indicated
directions to push out the roller.
2. Mark the measuring point and draw out the string.
Measure the roller protrusion again while the roller
is pushed in.
3. Note the difference in the above measurements is
the standard roller-rocker arm pin clearance.
Should the clearance exceed the limit, replace the
rocker arm.
Valve Cap Wear
Inspect the valve cap surface contacting the rocker arm
using a dial gauge.
If wear exceeds the limit, replace the valve cap with a
new one.
Rocker Arm Roller and
Pin Clearance
mm (in)
Standard
Limit
0.040 — 0.084 (0.0016
— 0.0033)
0.5 (0.02)
N6A0155E
N6A0156E
Legend
1. Roller
2. Depth gauge
Valve Cap Worn
mm (in)
Limit
0.1 (0.004)
N6A0157E
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