Engine: Description and Operation

NOTE: This engine is a NON free-wheeling design.

Block
The cylinder block is an aluminum alloy with cast-in-place cast iron cylinder liners. High rigidity is provided by: ribs cast in the outer wall, a full length water jacket, structural oil pan and windage tray, and cross bolt type main bearing caps.

Crankshaft
A six throw, five weight crankshaft is supported by four main bearings with number two being the thrust bearing. The six separate connecting rod throws are an even-firing design which reduces torque fluctuations while a torsional vibration damper is used to control torsion caused vibration of the crankshaft. Rubber lipped seals are used at front and rear. The front seal is retained in the oil pump case and the rear is retained in a block-mounted housing.

Pistons And Connecting Rods
The pistons are made of a high strength aluminum alloy. Top land height has been decreased to reduce emissions. Piston skirts are coated with a solid lubricant for scuff resistance. Connecting rod is forged steel with an oil squirt hole and attaches to the piston with a full floating pin retained by lock rings.

Cylinder Head
The aluminum alloy cylinder heads feature crossflow type intake and exhaust ports. Valve guides and seat inserts are powdered metal. Valves are arranged in a "W', with each camshaft on center. To improve combustion speed the chambers are a compact spherical design with a squish area of approximately 30 percent of the piston top area. The cylinder heads are common to either cylinder bank by reversing the direction of installation.

Camshafts And Timing Drive
A single overhead camshaft per cylinder head provides valve actuation. The left camshaft accommodates a cam sensor pick-up wheel and is therefore longer. Each camshaft is supported by four bearing journals. Thrust for each camshaft is taken at a thrust plate attached to the rear of each cylinder head. Right and left camshaft driving sprockets are not interchangeable because of the cam sensor pick-up wheel on the left sprocket. The sprockets and the engine water pump are driven by a single notched timing belt. Camshaft bearing lubrication is provided via an oil feed passage through each rocker shaft pedestal dowel.

Rocker Arm Shafts
The shafts are tubular steel and are supported by several forged aluminum alloy pedestals, which are fastened to the cylinder head. Four shafts are used, one for each intake and exhaust rocker arm bank on each Cylinder head. The shafts are hollow to provide a duct for lubricating oil flow from the cylinder head to the valve mechanisms. One hollow dowel per pedestal is used to locate the pedestal to the cylinder head, orient the exhaust rocker shaft, and serve as a cam bearing oil feed passage.

Rocker Arms
Rocker arms are of light weight permanent mold aluminum alloy with a roller type follower operating against the camshaft. The valve actuating end of the rocker arms are machined to retain hydraulic lash adjusters, eliminating the need for manual valve lash adjustment.

Valves
Valves are made of highly heat-resistant steel and are chrome plated to prevent stem scuffing. The intake valve is a one-piece forging, while the exhaust valve has a forged head with a welded stem for lock groove hardenability. Both valves employ a three groove lock design.

Valve Springs
Valve springs are unique for intake versus exhaust. Both are made from chrome silicon alloy wire and incorporate a "bee-hive" design. Valve spring retainers and locks are common. The valve spring seat is integral with the valve stem oil seal, which incorporates a garter spring to maintain consistent lubrication control to the valve stem.

Intake Manifold
The composite intake manifold is a cross-flow type with long runners to improve air charge inertia. An active Secondary Runner Valve (SRV) opens during certain operating conditions to improve top end performance. A Manifold Tuning Valve (MTV) connects the plenums at specific engine speeds to maximize low RPM torque without reducing high RPM power.

Exhaust Manifolds
Exhaust manifolds are made of a low mass, thin walled, stainless steel cast alloy. The outlets are designed for V-Band clamp attachment of close coupled catalytic converters.

Engine Lubrication
System is a full-flow filtration, pressure feed type. The oil pump body is mounted to the engine block. The pump inner rotor is driven by the crankshaft. A windage tray, integral with the oil pan gasket, increases power by minimizing oil windage at high engine RPM.