The LX5 V6, is a 3.5 L (213.5 cu in) engine
incorporating two intake and two exhaust valves
per cylinder with individual cylinder head mounted
camshafts for intake and exhaust functions
(DOHC). The cylinder bore diameter is 89.5 mm
(3.52 in) and the piston stroke is 92 mm (3.62 in).
The cylinders are arranged in two banks of three
with a 90 degree included angle. The left (front)
bank of cylinders are number 2-4-6 and the right
(rear) bank cylinders are 1-3-5. Engine firing order
is 1-2-3-4-5-6. The crankshaft throws are split to
provide even firing pulses 120 degrees apart.
The cylinder block is constructed of aluminum alloy
by the die casting method and is constructed of
two sections, an upper and a lower crankcase, split
at the crankshaft center line. The grey cast iron
cylinder liners are cast with the upper crankcase.
The upper and lower crankcase sections are held
in alignment by four dowel pins. Once machined,
the sections must be kept together as a set.
Sealing between the crankcase halves consists of
a silicone rubber seal and a bead of anaerobic
sealant along each side. Since the lower crankcase
contains the lower main bearings, this casting
adds to the structural rigidity of the engine
assembly. Both upper and lower crankcases
incorporate oil drain back passages isolated from
the crankcase. These passages provide a direct
path from the cylinder heads to the oil pan in order
to prevent the needless aeration of the oil through
contact with the rotating components.
3.5L Engine Mechanical Operation
Camshaft Drive System
The four overhead camshafts are driven by three separate 8 mm
(0.315 in), single-row, fine pitch chains. The primary drive chain
connects the crankshaft with both large intake camshaft sprockets,
the balance shaft sprocket and the intermediate shaft sprocket.
The exhaust camshafts are driven by short chains from the intake
camshafts. Primary timing chain tension is held by a tensioner that
hydraulically applies pressure to a pivoting tensioner shoe/chain
guide. The hydraulic tensioner minimizes chain noise and provides
accurate valve action by keeping slack out of the chain and
continuously adjusting for chain wear. As the chain stretches from
wear, a ratchet mechanism inside the tensioner prevents the nylon
pad from retracting when the engine is turned off and engine oil
pressure ceases. The intake to exhaust camshaft chain tensioner
contains an internal spring that provides a constant load on the
secondary timing chains.
The cylinder heads are semi-permanent mold cast aluminum with
powdered metal valve seat inserts and valve guides. Two 31 mm
(1.220 in) intake valves and two 29 mm (1.142 in) exhaust valves
are actuated by roller finger followers pivoting on a stationary
hydraulic lash adjuster (SHLA). Separate intake and exhaust
camshafts are supported by four bearings machined into the
cylinder head with camshaft thrust taken by the first bearing. The
combustion chamber is roughly in the shape of a clover leaf with a
nominal volume of 56.0 cc and a centrally located spark plug.
Engine Cooling System
The coolant pump is bolted to the engine front cover and is driven
by the serpentine belt via a drive pulley. The water outlet collects
coolant from the cylinder head for delivery to the radiator. The
water crossover also provides important functions for the EGR
System. The coolant pump and its housing form an assembly
which is inseparable and serviced as one unit.
The induction manifold is a plastic, lost core casting with a
removable plastic sight shield cover. The manifold is sealed to the
cylinder heads via imbedded silicone rubber around the intake
ports. These gaskets are integral to the manifold and are designed
to last the life of the engine.
Right and Left Bank Designation
Right hand (RH) and Left hand (LH) designations through the
engine mechanical On-Vehicle Service section are viewed from
the rear of the engine (left side of the vehicle). In certain cases
where a location with respect to the vehicle is required, it will be
referred to as right side or left side as viewed from inside the
The crankshaft is a cast nodular iron design with four 70 mm (2.75
in) diameter main bearings. Crankshaft thrust is taken by the
number three main bearing. The position sensor, also known as
the reluctor wheel, is cast integrally with the crankshaft. The
crankshaft is internally balanced and incorporates a two piece
modular rear seal. The connecting rod journals are 55.455 mm
(2.18 in) diameter. A rolled fillet radius is incorporated on all
bearing journals to improve fatigue strength.
Connecting Rods and Pistons
The connecting rods are forged powdered metal with 59.144 mm
(2.32 in) journals and have full floating piston pins. The connecting
rod's crankpin end incorporates fractured joint technology which
means the rod cap is "cracked" away from the once one-piece
connecting rod. The cap then becomes perfectly matched at the
cap to rod joint which significantly increases the strength of this
joint and the rod itself. The piston pins are slip fit in the bronze
bushed rods and are retained in the piston by round wire retainers.
The cast aluminum pistons use two low tension compression rings
and one multi-piece oil ring. The top compression ring is steel and
the second compression ring is coated cast iron. The oil ring is a
three piece side seal type ring which incorporates a steel expander
and two chrome plated steel rails. To provide a non-scuffing
surface when the engine is new, the pistons are tin plated and the
top land is anodized.