Lexus SC300 / Lexus SC400. Manual - part 370

D.  Inspect camshaft bearings

Check that bearings for flaking and scoring.
If the bearings are damaged, replace the bearing caps and
cylinder head a set.

E.  Inspect camshaft gear spring

Using a vernier caliper measure the free distance between
the spring ends.

Free distance:

18.2 – 18.8 mm (0.712 – 0.740 in.)

If the free distance is not as specified, replace the gear
spring.

F. 

Inspect camshaft journal oil clearance

(a)  Clean the bearing caps and camshaft journals.
(b)  Place the camshafts on the cylinder head.
(c)  Lay a strip of Plastigage across each of the camshaft

journals.

(d)  Install the bearing caps.

(See step 7 on pages 

EG–114

 to 120)

Torque: 16 N

⋅

m (160 kgf

⋅

cm, 12 ft

⋅

lbf)

NOTICE: Do not turn the camshaft.

(e)  Remove the bearing caps.

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EG–103

(f)  Measure the Plastigage at its widest point.

Standard oil clearance:

Exhaust camshaft thrust portion

0.025 – 0.061 mm (0.0010 – 0.0024 in.)

Others

0.030 – 0.067 mm (0.0012 – 0.0026 in.)

Maximum oil clearance:

0.10 mm (0.0039 in.)

If the oil clearance is greater than maximum, replace the cam-
shaft. If necessary, replace the bearing caps and cylinder
head as a set.

(g)  Completely remove the Plastigage.
(h)  Remove the camshafts.

G.

Inspect camshaft thrust clearance

(a)  Install the camshaft.

(See step 7 on pages 

EG–114

 to 120)

(b)  Using a dial indicator, measure the thrust clearance while

moving the camshaft back and forth.

Standard thrust clearance:

0.040 – 0.090 mm (0.0016 – 0.0035 in.)

Maximum thrust clearance:

0.12 mm (0.0047 in.)

If the thrust clearance is greater than maximum, replace the
camshaft. If necessary, replace the bearing caps and cylin-
der head as a set.

(c)  Remove the camshafts.

EG–104

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H.

Inspect camshaft gear backlash

(a)  Install the camshafts without installing the exhaust cam

sub–gear.
(See step 7 on pages 

EG–114

 to 120)

(b)  Using a dial indicator, measure the backlash.

Standard backlash:

0.020 – 0.200 mm (0.0008 – 0.0079 in.)

Maximum backlash:

0.30 mm (0.0188 in.)

If the backlash is greater then maximum, replace the cam-
shafts.

(c)  Remove the camshafts.

11.  INSPECT VALVE LIFTERS AND LIFTER BORES
(a) Using 

a 

caliper gauge, measure the ufter bore diameter of the

clinder head.

Lifter bore diameter:

31.000–31.016 mm (1.2205–1.2211 in.)

(b)  Using a micrometer, measure the lifter diameter.

Lifter diameter:

30.966 – 30.976 mm (1.2191 – 1.2195 in.)

(c)  Subtract the lifter diameter measurement from the lifter bore

diameter measurement.

Standard oil clearance:

0.024 – 0.050 mm (0.0009 – 0.0020 in.)

Maximum oil clearance:

0.07 mm (0.0028 in.)

If the oil clearance is greater than maximum, replace the lifter.
If necessary, replace the cylinder head.

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EG–105

12.  INSPECT AIR INTAKE CHAMBER

Using a precision straight edge and feeler gauge, measure
the surface contacting the intake manifold for warpage.

Maximum warpage:

0.15 mm (0.0059 in.)

If warpage is greater than maximum, replace the chamber.

13. INSPECT 

INTAKE 

MANIFOLD

Using a precision straight edge and feeler gauge, measure
the surface contacting the cylinder head and air intake cham-
ber for warpage.

Maximum warpage:

0.15 mm (0.0059 in.)

If warpage is greater than maximum, replace the manifold.

14.  INSPECT EXHAUST MANIFOLD

Using a precision straight edge and feeler gauge, measure
the surface contacting the cylinder head for warpage.

Maximum warpage:

1.00 mm (0.0394 in.)

If warpage is greater than maximum, replace the manifold.

15.  INSPECT CYLINDER HEAD BOLTS

Using a caliper gauge, measure the thread outside diameter
of the bolt.

Standard outside diameter:

9.770 – 9.960 mm (0.3846 – 0.3921 in.)

Maximum outside diameter:

9.60 mm (0.3780 in.)

If the diameter is less than minimum, replace the bolt.

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