3.8 ( 3800 ) V6 engine mechanical description
Starting at the front of the engine, the cylinders of the left bank are numbered 1-3-5
and the cylinders of the right bank are numbered 2-4-6. The crankshaft is
supported in the engine block by four bearings. The crankshaft is counterbalanced
by the flywheel, the crankshaft balancer, and the weights cast into the crankshaft.
Additional counterbalancing is obtained from the balance shaft which rides in the
engine block above the camshaft and is driven by the camshaft. All 3800 engines
are even-firing, the cylinders fire at equal 120 degree intervals of crankshaft
rotation. The location of the crankshaft journals has been offset by 30 degrees to
fire the cylinders at 120 degree intervals of crankshaft rotation. The camshaft lobes
and timing also reflect the 120 degree intervals. The even firing crankshaft provides
an equal interval of 120 degrees between ignition of each of the cylinders
throughout the firing order. The firing order is 1-6-5-4-3-2. The aluminum alloy
pistons have slipper skirts and are cam turned. Four drilled holes or casted slots in
the oil ring grooves permit drain back of the oil collected by the oil ring. The
camshaft is supported by four bearings in the engine block and is driven by the
crankshaft through sprockets and a timing chain. The cylinder heads are cast iron
and incorporate integral valve stem guides. Right and left cylinder heads are
identical and are interchangeable, but it is good practice to reinstall the cylinder
heads on the side from which they are removed. The intake manifold is bolted to the
inner faces of both cylinder heads so it connects with all inlet ports.
Each exhaust and intake valve has a valve spring to insure positive seating
throughout the operating speed range. The valve rocker arms for each bank of the
cylinders pivot on pedestals bolted to the cylinder head. Hydraulic roller valve lifters
and tubular push rods are used to operate overhead rocker arms and valves of
both banks of the cylinders from a single camshaft. This system requires no lash
adjustment at the time of assembly or service.
In addition to its normal function of a cam follower, each valve lifter also serves as
an automatic adjuster which maintains zero lash in the valve train under all
operating conditions. By eliminating all lash in the valve train and also providing a
cushion of oil to absorb operating shocks, the valve lifter promotes quiet valve
operation. It also eliminates the need for periodic valve adjustment to compensate
for wear of parts. Oil is supplied to the valve lifter through a hole in the side of the
valve lifter body which indexes with a groove and a hole in the valve lifter plunger.
Oil is then metered past the oil metering valve in the valve lifter, through the push
rods to the valve rocker arms. When the valve lifter begins to move up the camshaft
lobe, the check ball is held against its seat in the plunger by the check ball spring
which traps the oil in the base of the valve lifter body below the plunger.
The plunger and the valve lifter body then raise as a unit, pushing up the push rod
to open the valve. The force of the valve spring which is exerted on the plunger
through the valve rocker arm and push rod, causes a slight amount of leakage
between the plunger and the valve lifter body. This leakage allows a slow escape of
trapped oil in the base of the valve lifter body. As the valve lifter rolls down the other
side of the camshaft lobe and reaches the base circle or valve closed position, the
plunger spring quickly moves the plunger back (up) to its original position. This
movement causes the check ball to open against the ball spring, and any oil inside
the plunger is drawn into the base of the valve lifter. This restores the valve lifter to
the zero lash.
and the cylinders of the right bank are numbered 2-4-6. The crankshaft is
supported in the engine block by four bearings. The crankshaft is counterbalanced
by the flywheel, the crankshaft balancer, and the weights cast into the crankshaft.
Additional counterbalancing is obtained from the balance shaft which rides in the
engine block above the camshaft and is driven by the camshaft. All 3800 engines
are even-firing, the cylinders fire at equal 120 degree intervals of crankshaft
rotation. The location of the crankshaft journals has been offset by 30 degrees to
fire the cylinders at 120 degree intervals of crankshaft rotation. The camshaft lobes
and timing also reflect the 120 degree intervals. The even firing crankshaft provides
an equal interval of 120 degrees between ignition of each of the cylinders
throughout the firing order. The firing order is 1-6-5-4-3-2. The aluminum alloy
pistons have slipper skirts and are cam turned. Four drilled holes or casted slots in
the oil ring grooves permit drain back of the oil collected by the oil ring. The
camshaft is supported by four bearings in the engine block and is driven by the
crankshaft through sprockets and a timing chain. The cylinder heads are cast iron
and incorporate integral valve stem guides. Right and left cylinder heads are
identical and are interchangeable, but it is good practice to reinstall the cylinder
heads on the side from which they are removed. The intake manifold is bolted to the
inner faces of both cylinder heads so it connects with all inlet ports.
Each exhaust and intake valve has a valve spring to insure positive seating
throughout the operating speed range. The valve rocker arms for each bank of the
cylinders pivot on pedestals bolted to the cylinder head. Hydraulic roller valve lifters
and tubular push rods are used to operate overhead rocker arms and valves of
both banks of the cylinders from a single camshaft. This system requires no lash
adjustment at the time of assembly or service.
In addition to its normal function of a cam follower, each valve lifter also serves as
an automatic adjuster which maintains zero lash in the valve train under all
operating conditions. By eliminating all lash in the valve train and also providing a
cushion of oil to absorb operating shocks, the valve lifter promotes quiet valve
operation. It also eliminates the need for periodic valve adjustment to compensate
for wear of parts. Oil is supplied to the valve lifter through a hole in the side of the
valve lifter body which indexes with a groove and a hole in the valve lifter plunger.
Oil is then metered past the oil metering valve in the valve lifter, through the push
rods to the valve rocker arms. When the valve lifter begins to move up the camshaft
lobe, the check ball is held against its seat in the plunger by the check ball spring
which traps the oil in the base of the valve lifter body below the plunger.
The plunger and the valve lifter body then raise as a unit, pushing up the push rod
to open the valve. The force of the valve spring which is exerted on the plunger
through the valve rocker arm and push rod, causes a slight amount of leakage
between the plunger and the valve lifter body. This leakage allows a slow escape of
trapped oil in the base of the valve lifter body. As the valve lifter rolls down the other
side of the camshaft lobe and reaches the base circle or valve closed position, the
plunger spring quickly moves the plunger back (up) to its original position. This
movement causes the check ball to open against the ball spring, and any oil inside
the plunger is drawn into the base of the valve lifter. This restores the valve lifter to
the zero lash.
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