Lexus SC300 / Lexus SC400. Manual - part 369

(f)  Gradually heat the cylinder head to 80 – 100

C (176 –

212

F).

(g)  Using SST and a hammer, tap in a new guide bushing until

the snap ring makes contact with the cylinder head.
SST 09201–70010

(h) Using 

a 

sharp 6 mm reamer, ream the guide bushing to obtain

the standard specified clearance (See step 5 above)
between the guide bushing and valve stem.

7. 

INSPECT AND GRIND VALVES

(a)  Grind the valve enough to remove pits and carbon.
(b) Check 

that the valve is ground to the correct valve face angle.

Valve face angle:

44.5

°

(c)  Check the valve head margin thickness.

Standard margin thickness:

1.0 mm (0.039 in.)

Minimum margin thickness:

0.5 mm (0.020 in.)

If the margin thickness is less than minimum, replace the
valve.

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(d)  Check the valve overall length.

Standard overall length:

Intake

94.95 mm (3.7382 in.)

Exhaust

96.90 mm (3.8150 in.)

Minimum overall length:

Intake

94.45 mm (3.7185 in.)

Exhaust

96.40 mm (3.7953 in.)

If the overall length is less than minimum, replace the valve.

(e)  Check the surface of the valve stem tip for wear.

If the valve stem tip is worn, resurface the tip with a grinder
or replace the valve.

NOTICE: Do not grind off more than minimum.

8. 

INSPECT AND CLEAN VALVE SEATS

(a)  Using a 45

 carbide cutter, resurface the valve seats.

Remove only enough metal to clean the seats.

(b)  Check the valve seating position.

Apply a light coat of prussian blue (or white lead) to the valve
face. Lightly press the valve against the seat. Do not rotate
valve.

(c)  Check the valve face and seat for the following:

•

If blue appears 360

 around the face, the valve is

concentric. If not, replace the valve.

•

If blue appears 360

 around the valve seat, the guide

and face are concentric. If not, resurface the seat.

•

Check that the seat contact is in the middle of the valve
face with the following width:

1.0 – 1.4 mm (0.039 – 0.055 in.)

If not, correct the valve seats as follows:

(1)  If the seating is too high on the valve face, use 30

°

 and 45

°

cutters to correct the seat.

EG–100

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ENGINE MECHANICAL

(2)  If the seating is too low on the valve face, use 75

°

 and

45

°

 cutters to correct the seat.

(d) Hand–lap the valve and valve seat with an abrasive

compound.

(e)  After hand–lapping, clean the valve and valve seat.

9. INSPECT 

VALVE 

SPRINGS

(a)  Using a steel square, measure the deviation of the valve

spring.

Maximum deviation:

2.0 mm (0.079 in.)

If the deviation is greater than maximum, replace the valve
spring.

(b)  Using a vernier caliper, measure the free length of the valve

spring.

Free length:

43.6 mm (1.717 in.)

If the free length is not as specified, replace the valve spring.

(c) Using 

a 

spring tester, measure the tension of the valve spring

at the specified installed length.

Installed tension:

186 – 206 N (19.0 – 21.0 kgf, 41.9 – 46.3 lbf)

at 32.9 mm (1.295 in.)

If the installed tension is not as specified, replace the valve
spring.

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10.  INSPECT CAMSHAFTS AND BEARINGS
A.  Inspect camshaft for runout
(a)  Place the camshaft on V–blocks.
(b)  Using a dial indicator, measure the circle runout at the center

journal.

Maximum circle runout:

0.08 mm (0.0031 in.)

If the circle runout is greater than maximum, replace the cam-
shaft.

B.  Inspect cam lobes

Using a micrometer, measure the cam lobe height.

Standard cam lobe height:

Intake

41.710 – 41.810 mm (1.6421 – 1.6461 in.)

Exhaust

41.910 – 42.010 mm (1.6500 – 1.6539 in.)

Minimum cam lobe height:

Intake

41.56 mm (1.6362 in.)

Exhaust

41.76 mm (1.6441 in.)

If the cam lobe height is less than minimum, replace the cam-
shaft.

C.  Inspect camshaft journals

Using a micrometer, measure the journal diameter.

Journal diameter:

Exhaust camshaft thrust portion (A)

23.959 – 23.975 mm (0.9433 – 0.9439 in.)

Others

26.954 – 26.970 mm (1.0612 – 1.0618 in.)

If the journal diameter is not as specified, check the oil clear-
ance.

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