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Isuzu KB P190. Manual - part 750

Engine Mechanical – V6

Page 6A1–223

Cylinder Head Measurement

N O T E

For all cylinder head and associated component
specifications, refer to

5 Specifications

Camshaft Journal Clearance

Install the camshaft bearing cap in the cylinder head without the camshaft.

Install the camshaft cap bolts and tighten to the correct torque specification

Camshaft bearing cap attaching bolt........8.0 – 12.0 Nm.

Measure the camshaft bearings using an inside micrometer.

Subtract the camshaft journal diameter from the camshaft bearing diameter. This will provide the running
clearance. If the running clearance exceeds specifications and the camshaft journals are within specification,
replace the cylinder head.

Camshaft Journal Alignment

Ensure the camshafts are serviceable, refer to

3.19 Camshaft

for measuring procedures.

Inspect the cylinder head camshaft bearing surfaces for any imperfections or scratches that could inhibit correct
camshaft clearances. Repair minor imperfections or scratches.

Install the camshafts in the cylinder head.

Install the camshaft bearing caps.

Install the camshaft cap bolts and tighten to the correct torque specification.

Camshaft bearing cap attaching bolt........8.0 – 12.0 Nm.

Ensure the camshafts spin freely in the cylinder head. If the camshaft does not run freely, replace the cylinder
head.

Deck Flatness Inspection

Ensure the cylinder head decks are clean and free of
gasket material.

Inspect the surface for any imperfections or scratches
that could inhibit correct cylinder head gasket sealing.

Place a straight-edge (1) diagonally across the
cylinder head (2) deck face surface.

Measure the clearance between the straight-edge
and the cylinder head deck face using a feeler gauge
at four points along the straight-edge.

If the warpage is less than 0.05 mm, the cylinder
head deck surface does not require resurfacing.

If the warpage is between 0.05±0.20 mm or any
imperfections or scratches that could inhibit correct
cylinder head gasket sealing are present, the cylinder
head deck surface requires resurfacing.

If resurfacing is required the maximum amount that
can be removed is 0.25 mm.

If the cylinder head deck surface requires more than
0.25 mm material removal the head must be
replaced.

Figure 6A1 – 378

Engine Mechanical – V6

Page 6A1–224

Valve Guide Measurement

Measure the valve stem (1) to-guide (2) clearance.
Excessive valve stem-to-guide clearance may cause
excessive oil consumption and may also cause a
valve to break. Insufficient clearance will result in
noisy and sticky functioning of the valve and will
disturb the engine assembly smoothness.

Clamp a dial indicator to the cylinder head at the
camshaft cover rail.

Locate the dial indicator so the movement of the valve
stem from side to side, crossways to the cylinder
head, will cause a direct movement of the indicator
stem. The dial indicator stem must contact the side of
the valve stem just above the valve guide.

Drop the valve head about 0.064 mm off the valve
seat.

Use light pressure when moving the valve stem from
side to side to obtain a clearance reading, refer to

5 Specifications

•

If the clearance for the valve is greater than
specified and a new standard diameter valve
stem will not bring the clearance within
specifications, the valve guide may be oversized
by 0.075 mm using the valve guide reamer, Tool
No. J 42096 or by 0.375 mm using the valve
guide reamer, Tool No. EN-46120. Two sizes of
oversized valve stems are available for service.

•

Valve guide wear at the bottom 10 mm of the
valve guide is not significant enough to affect
normal operation.

•

If over sizing the guide does not bring the
clearance within specifications, replace the
cylinder head.

Figure 6A1 – 379

Engine Mechanical – V6

Page 6A1–225

Valve Spring Inspection and Measurement

Inspection Procedure

Clean the valve springs in solvent.

Safety glasses must be worn when using
compressed air

Dry the valve springs with compressed air.

Inspect the valve springs for broken coils or coil ends.

Measurement Procedure

Use a commercially available valve spring tester
to measure the valve spring tension, refer to

5 Specifications

CAUTION

Do not use shims to increase spring load.
The use of shims can cause the valve spring
to bottom out before the camshaft lobe is at
peak lift.

If low valve spring load is found, replace the valve
springs.

Figure 6A1 – 380

Valve and Seat Grinding

Valve Cleaning Procedure

CAUTION

Do not use a wire brush on any part of the
valve stem. The valve stem is chrome plated
to provide enhanced wear characteristics.
Wire brushing the stem could remove the
chrome plating.

Use soft bristle brush to clean any carbon build-up from the valve head.

Thoroughly clean the valve with solvent and wipe dry.

Engine Mechanical – V6

Page 6A1–226

Valve Visual Inspection Procedure

Inspect the valve for damage from the head to tip for
the following conditions:
•

pitting in the valve seat area (1),

•

lack of valve margin (2),

•

bending in the valve stem (3),

•

pitting or excessive wear in the stem (4),

•

worn valve key grooves (5), and

•

worn valve tip (6).

Replace the valve if any of these conditions exist.

Figure 6A1 – 381

Valve Measurement and Reconditioning Overview

Correct valve service is critical to engine performance. Therefore, all detailed measurement procedures must be followed
to identify components that are out of specification. If the measurement procedures reveal the valve or valve seat must
be reconditioned, it is critical to perform the measurement procedures after reconditioning.

Valve Seat Width Measurement Procedure

Measure the valve seat (1) width in the cylinder head
using a scale (2).

Figure 6A1 – 382

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