Chrysler Stratus RHD 1997 Interactive Electronic Service Manual page 938

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DESCRIPTION AND OPERATION (Continued)
the oil pump case and the rear is retained in a die-
cast aluminum block-mounted housing.
PISTONS
Are aluminum alloy with cast in steel struts at the
pin bosses for autothermic control. The piston head is
designed with valve recesses to provide for valve
clearance. The piston rings consist of a chrome-
plated, barrel faced design for the top ring, the sec-
ond ring is a cast iron tapered face design and the oil
ring is a chrome faced three piece design. Piston pins
are press-fitted into place, to join the pistons to the
forged steel connecting rods. The large end of the
connecting rod has a oil jet hole for lubrication of the
thrust side of the cylinder.
CYLINDER HEAD
The aluminum alloy cylinder heads feature a pent-
roof design with four valves per cylinder. Valve
guides are made of cast iron alloy and seat inserts
are made of sintered alloy iron, these are pressed
into the head. To improve combustion efficiency the
chambers have a compact pent-roof design with a
squish area. The cylinder heads are common to
either cylinder bank.
CAMSHAFTS
Two overhead camshafts provide valve actuation,
one left (radiator side of cylinder bank) and one
right. The distributor is directly driven by the right
camshaft. Both camshafts are supported by four
bearing journals intregal with the head. A flange at
the rear of the camshaft acts as a thrust collar. Right
and Left camshaft driving sprockets are interchange-
able. The sprockets and the engine water pump are
driven by the timing belt.
ROCKER ARM SHAFTS
The shafts are retained by retaining caps and
bolts. Four shafts are used, one for each intake and
exhaust rocker arm assembly on each cylinder head.
The hollow shafts provide a duct for lubricating oil
flow from the cylinder head to the valve mechanisms.
Rocker shaft springs are use on the intake shafts
ONLY to obtain the proper clearance between the
intake rocker arms and the spark plug tubes.
ROCKER ARMS
Are of light weight die-cast with roller type fol-
lower operating against the camshaft. The valve
actuating end of the rocker arms are machined for
hydraulic lash adjusters, eliminating the need for
periodic valve lash adjustment.
VALVES
Four valves per cylinder are actuated by die-cast
aluminum roller rocker arms and hydraulic lash
adjusters assemblies which pivot on rocker arm
shafts. All valves have 6 mm diameter chrome plated
valve stems. The valve train has 33 mm (1.299 inch)
diameter intake valves and 29 mm (1.141 inch) diam-
eter exhaust valves. The valves have a carbo-nitrid-
ing finish for long life. Fluorcarbon valve stem seals
are used on both valves. Stamped steel valve spring
seat, Valve springs, spring retainers, and locks are
conventional.
INTAKE MANIFOLD
This system is composed of a upper plenum (surge
tank) and manifold. This aluminum alloy manifold
has long runners to improve inertia. The plenum
chamber (surge tank) absorbs air pulsations created
during the suction phase of each cylinder. The lower
intake manifold is machined for six injectors and fuel
rail mounting.
EXHAUST MANIFOLDS
Both manifolds are made of cast nodular graphite
iron for heat resistance. Exhaust gasses from the left
cylinder bank, leave the left manifold through a
stainless steel pipe and bellows routed under the
engine to the right side manifold. The collected
exhaust from both manifolds are combined, and exit
to the exhaust pipe through a flex-joint.
DIAGNOSIS AND TESTING
CHECKING ENGINE OIL PRESSURE
Check oil pressure using gauge at oil pressure
switch location. Oil pressure should be 41 kPa (6
psi.) at idle or 241 to 517 kPa (35 to 75 psi.) at 3000
RPM.
(1) Remove pressure sending unit and install oil
pressure gauge.
CAUTION: If oil pressure is 0 at idle, Do Not Run
engine at 3000 RPM.
(2) Warm engine at high idle until thermostat
opens.
SERVICE PROCEDURES
BORING CYLINDER
Examine cylinder walls for scuffs, scoring and mea-
sure cylinder bore for out-of-round or taper. If defec-
tive, bore cylinder to oversize. Measure at points
shown in (Fig. 3).
Four oversize pistons are available (0.25mm (.010
inch) 0.50mm (.020 inch) 0.75mm (.030 inch) and
1.0mm (.039 inch). Determine oversize piston on
basis of largest cylinder bore.
2.5L ENGINE 9 - 101