1991 LEXUS SC400 length

The 1 UZ±FE engine has 8±cylinders in a V±arrangement at a bank an\
gle of 905. From the front of the RH
bank cylinders are numbered 2±4±6±8, and from the front of the LH b\
ank cylinders are numbered 1 ±3±5±7.
The crankshaft is supported by 5 bearings specified by the inside of the cr\
ankcase. These bearings are made
of a copper and lead alloy. The crankshaft is integrated with 8 weights which are cast along with it\
for balancing. Oil holes are built
into the center of the crankshaft for supplying oil to the connecting ro\
ds, pistons and other components. The ignition order is 1±8±4±3±6±5±7±2. The cylinder\
head is made of aluminum alloy, with a cross flow
type intake and exhaust layout and with pent±roof type combustion chambers. The spark plugs are loca\
ted in
the center of the combustion chambers.
At the front and rear of the intake manifold, a water passage has been p\
rovided which connects the RH
and LH cylinder heads. Exhaust and intake valves are equipped with irregular pitch springs made\
of special valve spring carbon
steel which are capable of following no matter what the engine speed.
The RH and LH intake camshafts are driven by a single timing belt, and a ge\
ar on the intake camshaft en-
gages with a gear on the exhaust camshaft to drive it. The camshaft jour\
nal is supported at 5 (intake) or 4 (ex-
haust) places between the valve lifters of each cylinder and on the front end of the cylinder \
head. Lubrication
of the cam journal gear is accomplished by oil being supplied through the \
oiler port in the center of the camshaft. Adjustment of the valve clearance is done by means of an outer shim type\
system, in which valve adjusting
shims are located above the valve lifters. This permits replacement of the sh\
ims without removal of the cam-
shafts. Pistons are made of high temperature±resistant aluminum alloy, and a depression is built into the piston
head to prevent interference with valves.
Piston pins are the full±floating type, with the pins fastened to neither the piston boss nor the connecting
rods. Instead, snap rings are fitted on both ends of the pins, preventing the\
pins from falling out. The No.1 compression ring is made of steel and the No.2 compression ring\
is made of cast iron. The oil
ring is m ade of a combination of steel and stainless steel. The outer diameter of\
each piston ring is slightly larger
than the diameter of the piston and the flexibility of the rings allows them\
to hug the cylinder walls when they
are mounted on the piston. Compression rings No.1 and No.2 work to prevent \
the leakage of gas from the cylin-
der and the oil ring works to scrape oil off the cylinder walls to prevent it from entering the combustion chamber. The cylinder block is made of aluminum alloy with a bank angle of 90 5. Cast iron cylinders are installed
inside the cylinder block. It has 8 cylinders which are approximately twice the length of th\
e piston stroke. The
top of each cylinder is closed off by the cylinder heads and the lower end of the cylinders becomes the crank-
case, in which the crankshaft is installed. In addition, the cylinder bl\
ock contains a water jacket, through which
coolant is pumped to cool the cylinders. The No.1 and No.2 oil pans are bolted onto the bottom of the cylinder block\
. The No.1 oil pan is made of
aluminum alloy. The No.2 oil pan is an oil reservoir made of pressed steel sheet. An o\
il level sensor is installed
in the No.1 oil pan (If the oil level drops below a set level, a warnin\
g light lights up.). A oil pan baffle plate keeps
sufficient oil in the bottom of the No.2 oil pan even when the vehicle is tilted. \
This dividing plate also prevents
the oil from making waves when the vehicle is stopped suddenly and the oil \
shifts away from the oil pump suction
pipe. Plastic region tightening bolts are used for the cylinder head, main bearing ca\
p and connecting rod.
EM±4
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ENGINE MECHANICAL Operation
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(b) Install a new gasket and throttle body with the two boltsand two nuts.
Torque: 18 N Vm (185 kgf Vcm, 13 ft Vlbf)
HINT: Use bolts 40 mm (1.57 in.) in length.
(c) Install the water by±pass pipe (from rear water by±pass
joint) to the clamp on the engine wire cover.
(d) Connect the following hoses: (1) Water by±pass hose to the ISC valve
(2) (USA Spec.) Vacuum hose to throttle body
(3) (Exc. USA Spec.) Three vacuum hoses to throttle body
(e) Connect the following connectors: (1) Throttle position sensor connector
(2) (w/ TRAC) Sub±throttle position sensor connector
(3) (w/ TRAC) Sub±throttle actuator
27. REINSTALL HEATER WATER VALVE (a) Install the water valve and bracket assembly with thetwo bolts.
(b) Install the engine wire clamp with the bolt.
(c) Connect the VSV connector.
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ENGINE MECHANICAL Engine Tune±Up
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28. REINSTALL RH NO.3 TIMING BELT COVER(a) Install the three gaskets to the timing belt cover.
(b) Fit portion A of the timing belt cover, matching it with the
lower high±tension cord cover.
(c) Install the timing belt cover with the three bolts.
29. REINSTALL VSV FOR EVAP SYSTEM Install the VSV with the two bolts.
30. REINSTALL LH NO.3 TIMING BELT COVER (a) Install the three gaskets to the timing belt cover.
(b) Install the cord grommet to the high±tension cord.
(c) Install the cord grommet to the timing belt cover.
(d) Fit portion A of the timing belt cover, matching it with the
lower high±tension cord cover.
(e) Install the timing belt cover with the three bolts.
31. RECONNECT PCV HOSE TO LH CYLINDER HEAD
32. RECONNECT FUEL RETURN HOSE TO FUEL RETURN PIPE
33. RECONNECT FUEL INLET HOSE TO LH DELIVERY PIPE Connect the inlet hose with two new gaskets and the
pulsation damper.
SST 09612±24014 (09617±24011)
Torque: 39 N Vm (400 kgf Vcm, 29 ft Vlbf)
33 N Vm (340 kgf Vcm, 24 ft Vlbf) for SST
HINT: Use a torque wrench with a fulcrum length of 30 cm
(11.81 in.)
34. REINSTALL RH ENGINE WIRE COVER (a) Fit portions A and B of the engine wire cover, matchingthem with the lower high±tension cord cover and No.3
timing belt cover.
(b) Install the engine wire cover with the bolt.
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ENGINE MECHANICAL Engine Tune±UpEM±25
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7. INSTALL NO.1 TIMING BELT COVER(a) Install the gasket to the timing belt cover.
(b) Install the timing belt cover with the four bolts.
8. INSTALL HYDRAULIC PUMP (a) Install the hydraulic pump and solenoid valve connectorclamp and engine speed sensor wire clamp with the two
bolts and two nuts.
Torque:
12 mm heads 16 N Vm (160 kgf Vcm, 12 ft Vlbf)
Others 30 N Vm (310 kgf Vcm, 22 ft Vlbf)
HINT: Each bolt length is indicated in the illustration.
Bolt length:
A 106 mm (4.17 in.) for 12 mm head
B 114 mm (4.49 in.) for 14 mm head
(b) Connect the solenoid valve connector.
9. INSTALL CRANKSHAFT PULLEY (a) Align the pulley set key on the crankshaft with the keygroove of the pulley.
(b) Using SST and a hammer, tap in the pulley.
SST 09223±46011
(c) Using SST, install and torque the pulley bolt.
SST 09213±70010 and 09330±00021
Torque: 245 N Vm (2,500 kgf Vcm, 181 ft Vlbf)
10. INSTALL RH CAMSHAFT TIMING PULLEY
(a) Align the knock pin on the camshaft with the knock pingroove of the timing pulley.
(b) Slide the timing pulley, facing the ºRº mark forward.
(c) Using SST, install and torque the pulley bolt.
SST 09278±54012
Torque: 108 N Vm (1,100 kgf Vcm, 80 ft Vlbf)
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ENGINE MECHANICAL Timing Belt
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19. INSTALL DRIVE BELT TENSIONERInstall the tensioner with the bolt and two nuts.
Torque: 16 N Vm (160 kgf Vcm, 12 ft Vlbf)
HINT: Use bolt 106 mm (4.17 in.) in length.
20. INSTALL ALTERNATOR (a) Install the alternator and A/T oil cooler pipe bracket withthe bolt and nut.
Torque: 37 N Vm (380 kgf Vcm, 27 ft Vlbf)
(b) Connect the alternator connector.
(c) Connect the alternator wire with the nut and cap.
21. INSTALL RH DISTRIBUTOR HOUSING (a) Install the distributor housing with the three bolts.
Torque: 18 N Vm (185 kgf Vcm, 13 ft Vlbf)
HINT:
w The RH distributor housing is marked with ºRº.
w Each bolt length is indicated in the illustration.
Bolt length: A 38 mm (1.50 in.)
B 96 mm (3.78 in.)
(b) Connect the cam position sensor connector.
22. INSTALL LH DISTRIBUTOR HOUSING (a) Install the distributor housing with the three bolts.
Torque: 18 N Vm (185 kgf Vcm, 13 ft Vlbf)
HINT:
w The LH distributor housing is marked with ºLº.
w Each bolt length is indicated in the illustration.
Bolt length: A 38 mm (1.50 in.)
B 80 mm (3.15 in.)
23. INSTALL DISTRIBUTOR ROTORS (a) Align the protrusion of the distributor rotor with thegroove of the camshaft timing pulley.
(b) Install the distributor rotor with the two bolts. Install the two distributor rotors.
Torque: 3.8 N Vm (39 kgf Vcm, 34 in. Vlbf)
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ENGINE MECHANICAL Timing Belt
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24. INSTALL DISTRIBUTOR CAPSInstall the distributor cap with the three bolts. Install the two
distributor caps.
Torque: 3.8 N Vm (39 kgf Vcm, 34 in. Vlbf)
25. INSTALL RH NO.2 TIMING BELT COVER
(a) Install the four gaskets to the timing belt cover.
(b) Install the connector grommet to the timing belt cover.
(c) Install the timing belt cover with the five bolts.
Torque (12 mm head bolt):
16 NVm (160 kgf Vcm, 12 ft Vlbf)
HINT (12 mm head bolt): Use bolts 106 mm (4.17 in.) in
length.
(d) Install the wire clamp to the timing belt cover.
(e) Install the cam position sensor connector to the ignition
coil bracket.
26. INSTALL LH NO.2 TIMING BELT COVER (a) Install the two gaskets to the timing belt cover.
(b) Run the cam po sition sensor wire through the timing belt
cover hole.
(c) Install the timing belt cover and connector bracket with the three bolts.
(d) Connect the cam position sensor connector.
(e) Install cam position sensor c onnector to connector
bracket.
(f) Install the connector grommet to the timing belt cover hole.
27. INSTALL DRIVE BELT IDLER PULLEY Install the idler pulley and cover plate with the pulley bolt.
Torque: 37 N Vm (380 kgf Vcm, 27 ft Vlbf)
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ENGINE MECHANICAL Timing BeltEM±53
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(e) Using a sharp 6 mm reamer, ream the guide bushing toobtain the standard specified clearance (See page
EM±45) 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 faceangle.
Valve face angle: 44.5 5
(c) Check the valve head margin thickness.
Standard margin thickness: 0.8±1.2 mm
(0.031±0.047 in.)
Minimum margin thickness: 0.5 mm (0.020 in.)
If the margin thickness is less than minimum, replace the
valve.
(d) Check the valve overall length.
Standard overall length: Intake 98.29±98.79 mm (3.8697±3.8894 in.)
Exhaust 98.84±99.34 mm (3.8657±3.9110 in.)
Minimum overall length: Intake 98.19 mm (3.8657 in.)
Exhaust 98.74 mm (3.8874 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 the minimum overall
length.
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ENGINE MECHANICAL Cylinder Head
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(d) Hand±lap the valve and valve seat with an abrasivecompound.
(e) After hand±lapping, clean the valve and valve seat.
9. INSPECT VALVE SPRINGS (a) Using a steel square, measure the squareness of thevalve spring.
Maximum squareness: 2.0 mm (0.079 in.)
If deviation is greater than maximum, replace the valve
spring.
(b) Using vernier calipers, measure the free length of the
valve spring.
Free length:
Pink painted mark 41.74 mm (1.6433 in.)
White painted mark 41.50 mm (1.6339 in.)
If the free length is not as specified, replace the valve spring.
(c) Using a spring tester, measure the tension of the valvespring at the specified installed length.
Installed tension:
186±206 N (19±21 kgf, 42±46 lbf) at 34.5 mm (1.358 in.)
If the installed tension is not as specified, replace the valve
spring.
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.
EM±48
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ENGINE MECHANICAL Cylinder Head
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