GM Service Manual Online
For 1990-2009 cars only

Engine Construction

The engine is a four cylinder in-line, four stroke gasoline unit with a Single Overhead Cam (SOHC) valve mechanism arranged for V-type valve configuration.

The SOHC is mounted over the cylinder head and is driven by the crankshaft through the timing belt. In this configuration there should be no push rods provided in the valve train system.


Object Number: 166125  Size: MF

Cylinder Head and Valve Train

The cylinder head is made of a cast aluminum alloy and has four in-line combustion chambers. Each combustion chamber has 2 intake valves and 2 exhaust valves.

A fuel injector is positioned near each set of intake valves. During each intake stroke of the engine, a fuel injector sprays or atomizes fuel into a fine mist. This mist mixes with air drawn in through the intake manifold as the piston reaches the bottom of the cylinder during the intake stroke.


Object Number: 166139  Size: SH

The valve train is driven by a single overhead camshaft. The camshaft has sixteen cam lobes. Each cam lobe operates an intake or exhaust valve through a rocker arm. Valve lash can be adjusted by turning the adjusting screw on the rocker arm after loosening the locknut. This will increase or decrease clearance between the rocker arm and the valve stem.

Cylinder Block

The cylinder block is made of cast aluminum alloy and has four cylinders arranged in-line. A cylindrical cast iron sleeve is installed in each cylinder. Engine coolant is circulated through the water jackets which surround the each sleeve keeping the engine operating temperature constant.

Crankshaft and Main Bearings

A monoblock casting crankshaft is supported by five main bearings. It has an eight-piece type counter weight which is incorporated with the balance weight. The four crankpins on the crankshaft are positioned 180 degrees apart. The bearing caps incorporate bearing cap supports.

Pistons, Rings, Piston Pins and Connecting Rods

Each piston is cast aluminum alloy and has two compression rings and one oil ring. The top compression ring is plated with hard chromium for improvement in abrasion resistance. The oil ring consists of two rails and one spacer.

The piston pin is offset 0.5 mm (0.02 in) toward the thrust side. This allows a gradual change in travels through the bore. Piston pins are chromium steel and have a floating fit in the pistons and partially in the connecting rods. The connecting rods are made of forged steel and the rod bearings are of the precision insert type.