1991 LEXUS SC400 Service Repair Manual

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Page 2881 of 4087

LEXUS SC400 1991 Service Repair Manual
SERVICE SPECIFICATIONS
SERVICE DATA
VSVResistance30±34
for EVAP
VSVResistance33±39
for EGR
EGR valveResistance19.9±23.4
(CALIF. only)
TORQUE SPECIFICATIONS
Part tightenedNVmkgf Vcmft Vlbf
V

Page 2882 of 4087

LEXUS SC400 1991 Service Repair Manual
ENGINE MECHANICAL
NOTE: The specification descriptions ºUSA Spec.º and
º Exc. USA Spec. º used in this section indicate the following
specifications.
USA Spec .: USA (50 States) Specifications.
E

Page 2883 of 4087

LEXUS SC400 1991 Service Repair Manual
DESCRIPTION
The 1 UZ±FE engine is an V±8 4.0 liter DOHC 32 valve engine.
OPERATION
EM±2±
ENGINE MECHANICAL Description, Operation
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Page 2884 of 4087

Page 2885 of 4087

LEXUS SC400 1991 Service Repair Manual
±
ENGINE MECHANICAL OperationEM±3
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Page 2886 of 4087

$LEXUS SC400 1991 Service Repair Manual The 1 UZ±FE engine has 8±cylinders in a V±arrangement at a bank an\ gle of 905. From the front of the RH bank cylinders are numbered 2±4±6±8, and from the front of the LH b\ ank cylinders are n$

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
±
ENGINE MECHANICAL Operation
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Page 2887 of 4087

LEXUS SC400 1991 Service Repair Manual
PREPARATION
SST (SPECIAL SERVICE TOOLS)
±
ENGINE MECHANICAL PreparationEM±5
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Page 2888 of 4087

LEXUS SC400 1991 Service Repair Manual
SST (SPECIAL SERVICE TOOLS) (Contd)
RECOMMENDED TOOLS
EM±6±
ENGINE MECHANICAL Preparation
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