Toyota Supra 1990 Manual page 35

ENGINE MECHANICAL - Description
EM-3
The 7M-GE, 7M-GTE engines are an in-line
6-cylinder engine with the cylinders numbered
1-2-3-4-5-6 from the front. The crankshaft is sup-
ported by 7 bearings specified by the inside of the
crankcase. These bearings are made of kelmet.
The crankshaft is integrated with 1 2 weights
which are cast along with it for balance. Oil holes
are built into the crankshaft for supplying oil to the
connecting rods, pistons and other components.
These engine's ignition order is 1-5-3-6-2-4. 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 located in the center of the combustion
chambers.
Exhaust and intake valves are equipped with ir-
regular pitch springs with symmetrical ends made
of oil tempered silicon chrome steel wire which are
capable of following the valves even at high engine
speeds.
Both the exhaust side cam shaft and the intake
side cam shaft are driven by a single timing belt.
The cam journal is supported at 7 places between
the valve lifters of each cylinder and on the cylinder
head of front end. Lubrication of the cam journal
and cam is accomplished by oil being supplied
through the oiler port in the center of the camshaft.
Adjustment of the valve clearance is done by me-
ans 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.
The resin timing belt cover is made in 2 pieces.
Pistons are made of high temperature-resistant
aluminum alloy, and depressions are 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 connect-
ing 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 stainless
steel and the No.2 compression ring is made of cast
iron. The oil ring is made of a combination of stain-
less 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 pre-
vent the leakage of gas from the cylinder 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 cast iron. It has 6
cylinders which are approximately 1.6 times the
length of the piston stroke. The top of the cylinders
is shut off by the cylinder head and the lower end
of the cylinders becomes the crankcase, 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 oil pan is bolted to the bottom of the cylinder
block. The oil pan is an oil reservoir made of pressed
steel sheet. A dividing plate is included inside the
oil pan to keep sufficient oil in the bottom of the
pan even when the vehicle is tilted. This dividing
plate also prevents the oil from making waves when
the vehicle is stopped suddenly and thus shifting
the oil away from the oil pump suction pipe.