Toyota 3S-GE Repair Manual page 18

EG4
ENGINE — ENGINE MECHANICAL
The 3S—GE engine is an in—line, 4 cylinder engine with the cylinders numbered I — 2 — 3 -— 4
from the front. The crankshaft is supported by 5 bearings inside the crankcase. These bearings
are made of aluminum 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 I — 3 —— 4 — 2. The cylinder head is made of 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.
The intake manifold has 4 independent long ports and utilizes the inertial supercharging effect to
improve engine torque at low and medium speeds.
Both the intake camshaft and the exhaust camshaft are driven by a single timing belt. The cam
journal is supported at 5 places between the valve lifters of each cylinder and on the front end of
the cylinder head. Lubrication of the cam journals and cams 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 inner shim type system, in which valve
adjusting shims are located below the valve lifters. To replace the shims, the camshafts must be
removed.
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 stainless steel and the No.2 compression ring is made of
cast iron. The oil ring is made of 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 combustion chambers.
The cast iron cylinder block has 4 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 crankcase, in which the crankshaft is installed. In addition, the cylinder
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 the cylinder block. The No.1 oil pan is
made of alumimum alloy. The No.2 oil pan is an oil reservoir made of pressed sheet steel. The
dividing plate also prevents the oil from shifting away from the oil pump suction pipe when the
vehicle is stopped suddenly.