Low Speed Operation

WARNING: This page is about a different car, the 2007 Saturn Vue. However, it is still accessible from the selected car via links, so may be relevant.

Fig 1: View Of Primary & Secondary Rocker Arms

Courtesy of GENERAL MOTORS CORP.

The primary (4) and secondary (2) rocker arms are not connected to the mid rocker arm (3) and are driven separately by the camshaft lobes (5 and 7). Even though the mid rocker arm (3) is following the center camshaft lobe (6), it has no effect on the opening and closing of the valves in the low RPM range. The valve lash adjuster (207) absorbs the lost motion action of the mid rocker arm.

Fig 2: View Of Engine Oil Flow Diagram

Courtesy of GENERAL MOTORS CORP.

The oil is pulled from the oil sump through the screen (405). Oil pressure generated in the oil pump (424) is supplied through the oil filter (410) to the engine block (100). The oil pressure is then directed to the cylinder heads (200) for rocker arm and camshaft lubrication. The oil restrictors (431) located within the upper engine block reduce the oil pressure to eliminate intake rocker arm piston actuation.