Lexus SC300 / Lexus SC400. Manual — part 419

(b) Check that the timing marks of the camshaft timing

pulleys and timing belt rear plates aligned.

If not, turn the crankshaft one revolution (360

°

) and align the

mark as above.

20. INSPECT

VALVE

CLEARANCE

(a) Check only those valves indicated.

•

Using a feeler gauge, measure the clearance
between the valve lifter and camshaft.

•

Record the out–of–specification valve clearance
measurements. 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.)

(b) Turn the crankshaft one revolution (360

°

), and align the

mark as above. (See procedure step in 19 (a))

(c) Check only the valves indicated as shown. Measure the

valve clearance.

(See procedure in step (a))

EM–16

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ENGINE MECHANICAL

Engine Tune–Up

21. REMOVE THEFT DETERRENT HORN

(a) Disconnect the connector.
(b) Remove the bolt and theft deterrent horn.
HINT: Remove the deterrent horn when the valve clearance
is adjusted for the front portion of the exhaust camshaft on
the LH cylinder head.

22. ADJUST

VALVE

CLEARANCE

(a) Remove the adjusting shim.

•

Turn the crankshaft, and position the cam lobe of
the camshaft on the adjusting valve upward.

•

Position the hole of the adjusting shim toward the
spark plug side.

•

Press down the valve lifter with SST (A), and place
SST (B) between the camshaft and valve lifter
flange. Remove SST (A).

SST 09248–55011

(09248–05011 (A), 09248–05021 (B))

NOTICE: The valve lifter is made of aluminum, which is
easily scratched. So when setting SST (B), take care not
to scratch the face of the valve lifter.

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ENGINE MECHANICAL

Engine Tune–Up

EM–17

Using compressed air and magnetic finger, remove

the adjusting shim by blowing air into the shim hole.

HINT: Remove the adjusting shim from the intake man-
ifold side.

NOTICE: Do not drop the adjusting shim into por-
tions A and B. If dropped into portion A, the adjust-
ing shim will pass through the cylinder head and
cylinder block into the oil pan. If dropped into por-
tion B, the adjusting shim cannot be recovered with-
out removing the exhaust camshaft.

inspNFO

EM–18

–

ENGINE MECHANICAL

Engine Tune–Up

(b) Determine the replacement adjusting shim size

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 (0.008 in.))
Exhaust N = T + (A–0.30 mm (0.012 in.))

•

Select a new shim with a thickness as close as
possible to the calculated values.

HINT: Shims are available in thirty–three sizes in increments
of 0.025 mm (0.0010 in.), from 2.50 mm (0.0984 in.) to 3.30
mm (0.1299 in.).
(c) Install a new adjusting shim.

•

Place a new adjusting shim on the valve lifter.

•

Press down the valve lifter with SST (A), and
remove SST (B).

SST 09248–55011
(d) Recheck the valve clearance.

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ENGINE MECHANICAL

Engine Tune–Up

EM–19