1991 LEXUS SC400 length

35. REMOVE CYLINDER HEAD COVERSRemove the 8 bolts, seal washers, cylinder head cover and
gasket. Remove the 2 cylinder head covers.
36. IF NECESSARY, REMOVE SEMI±CIRCULAR PLUGS
37. REMOVE CAMSHAFTS
NOTICE: Since the thrust clearance of the camshaft is small,
the camshaft must be kept level while it is being removed. If the
camshaft is not kept camshaft is not kept level, the portion of
the cylinder head receiving the shaft thrust may crack or be
damaged, causing the camshaft to seize or break. To avoid
this, the following steps should be carried out.
A. Remove exhaust camshaft from RH cylinder head
(a) Boring the service bolt hole of the driven sub±gear upward by turning the hexagon wrench head portion of the exhaust
camshaft with a wrench.
(b) Secure the exhaust camshaft sub±gear to the drive gear with
a service bolt.
Recommended service bolt: 6 mm for thread diameter
1.0 mm for thread pitch
16 ± 20 mm (0.63 ± 0.79 in.) for bolt length
HINT: When removing the camshaft, make sure that the tor-
sional spring force of the sub±gear has been eliminated by
the above operation.
(c) Set the timing mark (1 dot mark) of the camshaft driven gear at approx. 10
angle by turning the hexagon wrench head
portion of the exhaust camshaft with a wrench.
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C. Remove exhaust camshaft from LH cylinder head
(a) Boring the service bolt hole of the driven sub±gear upwardby turning the hexagon wrench head portion of the exhaust
camshaft with a wrench.
(b) Secure the exhaust camshaft sub±gear to drive gear with a service bolt.
Recommended service bolt:6 mm for thread diameter
1.0 mm for thread pitch
16 ± 20 mm (0.63 ± 0.79 in.) for bolt length
HINT: When removing the camshaft, make sure that the tor-
sional spring force of the sub±gear has been eliminated by
the above operation.
(c) Set the timing mark (2 dot marks) of the camshaft drive gear at approx. 15
angle by turning the hexagon wrench head
portion of the exhaust camshaft with a wrench.
(d) Alternately loosen and remove the 2 bearing cap bolts holding the intake camshaft side of the oil feed pipe to the
cylinder head.
(e) Uniformly loosen and remove the 8 bearing cap bolts in several passes, in the sequence shown.
(f) Remove the oil feed pipe, 4 bearing caps and ex haust
camshaft.
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(d) Check the valve overall length.
Standard overall length:Intake94.95 mm (3.7382 in.)
Exhaust 96.90 mm (3.8150 in.)
Minimum overall length:
Intake94.45 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: wIf blue appears 360
around the face, the valve is
concentric. If not, replace the valve.
w If blue appears 360
around the valve seat, the guide
and face are concentric. If not, resurface the seat.
w 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 5 and 45 5
cutters to correct the seat.
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(2) If the seating is too low on the valve face, use 755 and
45 5 cutters to correct the seat.
(d) H and±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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(d) RH Cylinder Head:Install the bearing cap (mark ª11º) in position with the arrow
mark facing rearward.
(e) LH Cylinder Head: Install the bearing cap (mark ª16º) in position with the arrow
mark facing forward.
(f) Install a new seal washer to the bearing cap bolt.
(g) Apply a light coat of engine oil on the threads of the bearing
cap bolt.
(h) Install the 4 bearing cap bolts. Alternately tighten bearing cap bolts.
Torque: 16 N Vm (160 kgf Vcm, 12 ft Vlbf)
HINT: Use silver colored bolts 38 mm (1.50 in.) in length.
6. ASSEMBLE EXHAUST CAMSHAFT
(a) Install the following parts: (1) Camshaft gear spring
(2) Camshaft sub±gear
(3) Wave washer
HINT: Align the pins on the gears with the spring ends.
(b) Using snap ring pliers, install the snap ring.
(c) Mount the hexagon wrench head portion of the camshaft in a vise.
NOTICE: Be careful not to damage the camshaft.
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(f) Install the other 4 bearing caps in the sequence shown withthe arrow marks facing rearward.
HINT: Align the arrow marks at the front and rear of the cylin-
der head with the mark on the bearing cap.
(g) Apply a light coat of engine oil on the threads and under the heads (A only) of the bearing cap bolts.
HINT: Do not apply engine oil under the heads of the bearing
cap bolt (B).
(h) Install a new seal washer to the bearing cap bolt (B). Install the 8 bearing cap bolts as shown.
HINT:
wUse bearing cap bolts 38 mm (1.50 in.) in length. The
bolts are black (A) or silver (B) in color. Install the 2 silver
bolts to the front bearing cap. Install the 6 black bolts to
the other positions.
w After installing the oil feed pipe, install the 2 bolts to rear
bearing cap as directed in step B (i).
(i) Uniformly tighten the 8 bearing cap bolts in several passes, in the sequence shown.
Torque: 16 N Vm (160 kgf Vcm, 12 ft Vlbf)
B. Install exhaust camshaft to RH cylinder head
(a) Set the timing mark (1 dot mark) of the camshaft drive gear
at 10
angle by turning the hexagon wrench head portion of
the intake camshaft with a wrench.
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(b) Apply MP grease to the thrust portion of the exhaustcamshaft.
(c) Align the timing marks (1 dot mark) of the camshaft drive and
driven gears.
(d) Place the exhaust camshaft on the cylinder head.
(e) Check that the exhaust camshaft moves smoothly in the thrust direction.
(f) Install the rear bearing cap (mark ªE1º) with the arrow mark facing rearward.
HINT:
wInstalling the rear bearing cap will determine the thrust
portion of the camshaft.
w Align the allow marks at the front and rear of the cylinder
head with the mark on the bearing cap.
(g) Install the other 3 bearing caps in the sequence shown with the arrow marks facing rearward.
HINT: Align the arrow marks at the front and rear of the cylin-
der head with the mark on the bearing cap.
(h) Apply a light coat of engine oil on the threads and under the heads of the bearing cap bolts.
(i) Install the oil feed pipe and 10 bolts.
HINT: Use bearing cap bolts 38 mm (1.50 in.) and 52 mm
(2.05 in.) in length. Use black colored 38 mm (1.50 in.) bolts.
Install the two 52 mm (2.05 in.) bolts in outside positions of
the oil feed pipe. Install the eight 38 mm (1.50 in.) bolts in the
other positions.
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(e) Install the front bearing cap (mark ª11º) with the arrow markfacing forward.
HINT:
wInstalling the front bearing cap will determine the thrust
portion of the camshaft.
w Align the allow marks at the front and rear of the cylinder
head with the mark on the bearing cap.
(f) Install the other 4 bearing caps in the sequence shown with the arrow marks facing rearward.
HINT: Align the arrow marks at the front and rear of the cylin-
der head with the mark on the bearing cap.
(g) Apply a light coat of engine oil on the threads and under the heads (A only) of the bearing cap bolts.
HINT: Do not apply engine oil under the heads of the bearing
cap bolt (B).
(h) Install a new seal washer to the bearing cap bolt (B). Install the 8 bearing cap bolts as shown.
HINT:
wUse bearing cap bolts 38 mm (1.50 in.) in length. The
bolts are black (A) or silver (B) in color. Install the 2 silver
bolts to the front bearing cap. Install the 6 black bolts to
the other positions.
w After installing the oil feed pipe, install the 2 bolts to the
bearing cap 2nd from the front as directed in step B (i).
(i) Uniformly tighten the 8 bearing cap bolts in several passes, in the sequence shown.
Torque: 16 N Vm (160 kgf Vcm, 12 ft Vlbf)
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