Lexus SC300 / Lexus SC400. Service manual — part 415
9. REMOVE NO. 3, NO. 1 AND NO. 2 CYLINDER HEAD
COVERS
(a) Remove the 12 bolts and four nuts.
(b) Remove the cylinder head covers and gaskets.
10. SET NO. 1 CYLINDER TO TDC/COMPRESSION
(a) Turn the crankshaft pulley and align its groove with
timing mark ”0” of the No. 1 timing belt cover.
NOTICE: Always turn the crankshaft clockwise.
(b) Check that the timing marks of the camshaft timing
pulleys are aligned with the timing marks of the No. 4
timing belt cover.
If not, turn the crankshaft one revolution (360
°
).
11. INSPECT
VALVE
CLEARANCE
(a) Uniformly tighten the bearing cap bolts in several
passes.
Torque: 20 N
⋅
m (200 kgf
⋅
cm, 14 ft
⋅
lbf)
(b) Check only those valves indicated in the illustration.
•
Using a feeler gauge, measure the clearance
between the valve lifter and camshaft.
•
Record the valve clearance measurements of
those that are out of specification. They will be used
later to determine the required replacement
adjusting shim.
Valve clearance (Cold):
Intake 0.15–0.25 mm (0.006–0.010 in.)
Exhaust 0.25–0.35 mm (0.010–0.014 in.)
EM–12
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ENGINE MECHANICAL
Engine Tune–Up
(c) Turn the crankshaft 2/3 of a revolution (240
), check
only the valves indicated in the illustration.
Measure the valve clearance.
[See procedure in step (b)]
(d) Turn the crankshaft a further 2/3 of a revolution (240
),
check only the valves indicated in the illustration.
Measure the valve clearance.
[See procedure in step (b)]
12. ADJUST
VALVE
CLEARANCE
(a) Remove the adjusting shim.
•
Turn the camshaft so that the cam lobe for the valve
to be adjusted faces up.
•
Turn the valve lifter with a screwdriver so that the
notches would be per pendicular to the camshaft.
•
Using SST (A), press down the valve lifter and
place SST (B) between the camshaft and valve
lifter. Remove SST (A).
SST 09248–55020
(09248–05011 (A), 09248–05021 (B))
HINT:
•
Choose either method A or B in using SST on either side
of the cam lobe.
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ENGINE MECHANICAL
Engine Tune–Up
EM–13
•
Position SST on the edge of the lifter for easy removal
of the shim.
•
Remove the adjusting shim with a small screwdriver and
a magnetic finger.
(b) Determine the replacement adjusting shim size
according to the following formula or Charts:
•
Using a micrometer, measure the thickness of the
removed shim.
•
Calculate the thickness of a new shim so the valve
clearance comes within specified value.
T
Thickness of used shim
A
Measured valve clearance
N
Thickness of new shim
Intake N = T + (A–0.20 mm)
Exhaust N = T + (A–0.30 mm)
•
Select a new shim with a thickness as close as
possible to the calculated values.
HINT: Shims are available in seventeen sizes in increments
of 0.05 mm, from 2.50 mm to 3.30 mm.
(c) Install a new adjusting shim.
•
Place a new adjusting shim on the valve lifter, with
imprinted numbers facing down.
•
Press down the valve lifter with SST (A), and
remove SST (B).
SST 09248–55020
(d) Recheck the valve clearance.
EM–14
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ENGINE MECHANICAL
Engine Tune–Up
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ENGINE MECHANICAL
Engine Tune–Up
EM–15
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