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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