Toyota 4A-FE Repair Manual page 11

ENGINE MECHANICAL - Description (4A-FE)
EM-3
The 4A-FE engine is an in-line 4-cylinder engine
with the cylinders numbered .1-2-3-4 from the
front. The crankshaft is supported by
5
specified
bearings inside the crankcase. These bearing are
made of aluminum alloy.
The crankshaft is integrated with
8
weights
which are cast with it for balane_ Oil holes are
made in the center of the crankshaft to supply oil
to the connecting rods, bearing, pistons and other
components_
The ignition order is 1 -3-4-2 . The cylinder head
is made of aluminum alloy, with a cross flow type
intake and exhaust layout with pent roof type
combustion chambers. The spark plugs are
located in the center of the combustion chamber.
The intake manifold has 4 independent long
ports and utilizes the inertial supercharging effect
to improve engine torque at low and medium
speeds.
Exhaust and intake valves are equipped with
irregular pitch springs made of special carbon steel
which are capable of functioning no matter what
the engine speed.
The exhaust side cam shaft is driven by a timing
belt, and a gear on the exhaust side cam shaft
engages with a gear on the intake side cam shaft
to drive it. 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 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 shims
without removal of the camshafts.
The resin timing belt cover is made of 3 pieces.
A service hole is provided in the No.1 belt cover
for adjusting the timing belt tension.
Pistons are made of highly temperature-resis-
tant aluminum alloy, and a depression is built into
the piston head to prevent interference with
valves.
Piston pins are the semi-floating type, with the
pins fastened to the connecting rods by pressure
fitting, allowing the pistons and pins to float.
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
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 cylinder and oil ring works to scrape oil off
the cylinder walls to prevent it from entering the
combustion chambers.
The cylinder block is made of cast iron. It has 4
cylinders which are approximately 2 times the
length of the piston stroke. The top of the cylin-
ders is closed 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
i~
included
inside the oil pan to keep .sufficient oil at the bot-
tom
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 suc-
tion pipe.
•