Lexus SC300 / Lexus SC400. Manual

The 1 UZ–FE engine has 8–cylinders in a V–arrangement at a bank angle of 90

. From the front of the RH

bank cylinders are numbered 2 – 4 – 6 – 8, and from the front of the LH bank cylinders are 1 – 3 – 5 – 7.
The crankshaft is supported by 5 bearings inside the crankcase. These bearings are made of a copper and
lead alloy.
The crankshaft is integrated with 8 weights for balance. Oil holes are placed in the center of the crankshaft
to supply oil to the connecting rods, bearing, pistons and other components.
The ignition order is 1 – 8 – 4 – 3 – 6 – 5 – 7 – 2. The cylinder head is made of alminum alloy, with a cross
flow type intake and exhaust layout and with pent–roof type combustion chambers. The spark plugs are
located in the center of the combustion chambers.
At the front and rear of the intake manifold, a water passage has been provided 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 functioning at all engine speeds.
The RH and LH intake camshaft are driven by a timing belt, and a gear on the intake camshaft engages
with a gear on the exhaust camshaft to drive it. The cam journal is supported at 5 (intake) or 4 (exhaust)
places between the valve lifters of each cylinder and on the front end of the cylinder head. Lubrication of
the cam journals and gears 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 shims without removal of the
camshafts.
Pistons are made of high temperature–resistant aluminum alloy, and a depression is built into the piston
head to prevent interference with the 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 made 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 gas leakage from
the cylinder and the oil ring works to scrape oil off the cylinder walls to prevent it from entering the combus-
tion chambers.
The cylinder block is made of aluminum alloy with a bank of 90

. Cast iron cylinders are installed inside

the cylinder block. It has 8 cylinders which are approximately twice the length of the piston stroke. The top
of each cylinder is closed off by the cylinder head and the lower end of the cylinders becomes the crank-
case, in which the crankshaft is installed. In addition, the cylinder block 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 oil level sensor is
installed in the No.1 oil pan (If oil level drops below a set level, a warning lights up.). And 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 marking waves when the vehicle is stopped suddenly and the oil shifts away from the
oil pump suction pipe.
Plastic region tighten bolts are used for the cylinder head, main bearing cap and connecting rod.

EG–4

–

1UZ–FE ENGINE

ENGINE MECHANICAL

Lexus SC300 / Lexus SC400. Manual - part 345