Engine Component Description. Buick Roadmaster 1996

For 1990-2009 cars

#### Engine Block

The engine block is cast iron. The engine block has eight cylinders arranged in a V shape with four cylinders in each bank. The engine block is a one piece casting. The cylinders are encircled by coolant jackets.

#### Cylinder Heads

The cylinder heads are cast iron. The cylinder heads have powdered metal valve guides and valve seats pressed into the intake and the exhaust ports.

#### Crankshaft

The crankshaft is cast nodular iron. Five crankshaft bearings support the crankshaft. The bearings are retained by bearing caps. The bearing caps are machined with the block for proper alignment and clearances. The bearing caps are retained by two bolts each. The number five bearing at the rear of the engine assembly is the end thrust bearing. Four connecting rod journals are spaced 90 degrees apart. There are two connecting rods in each journal. The crankshaft position sensor reluctor ring is pushed onto the front of the crankshaft . The reluctor ring has four lugs used for crankshaft timing and is constructed of powdered metal. The reluctor ring has a slight interference fit onto the crankshaft and an internal keyway for correct positioning.

#### Piston and Connecting Rod Assemblies

The pistons are cast aluminum. The pistons use two compression rings and one oil control assembly. The piston is a low friction, lightweight design with a flat top and barrel shaped skirt. The piston pins are chromium steel. They have a floating fit in the piston and are retained by a press fit in the connecting rod. The connecting rods are forged powdered metal. The connecting rods are machined with the rod cap installed for proper clearances and alignments.

#### Camshaft

The camshaft is steel. The camshaft is supported by five bearings pressed into the engine block. The camshaft timing chain sprocket mounted to the front of the camshaft is driven by the crankshaft sprocket thorough a camshaft timing chain.

The camshaft sprocket also has spur gear teeth which drive a geared shaft assembly to operate the water pump.

A spiral gear machined into the camshaft near the rear journal drives a shaft assembly which operates the oil pump driveshaft assembly.

A pin on the camshaft mates with the distributor driveshaft. This provides net build timing. This means that the ignition timing does have to be adjusted.

#### Valve Train

The valve train is a ball pivot type. Motion is transmitted from the camshaft through the hydraulic roller valve lifters and the tubular valve pushrods to the valve rocker arms. The valve rocker arm pivots on a ball in order to open the valve. The hydraulic valve lifters keep all the parts of the valve train in constant contact.

The valve rocker arm stud retains the valve rocker arm ball with a locking nut. The valve rocker arm studs are pressed into the cylinder head.

#### Intake Manifold

The intake manifold is a one-piece cast aluminum unit. The intake manifold has exhaust gas recirculation and crankcase vent passages cast into it. Coolant crossover passages have been eliminated.

#### Exhaust Manifolds

The two exhaust manifolds are cast iron. The exhaust manifolds direct exhaust gases from the combustion chambers to the exhaust system. The exhaust manifolds each have a port for air injection system pipe fittings.