A closed crankcase ventilation system is used in order to provide a more complete scavenging of crankcase vapors. Fresh air from the throttle body is supplied to the crankcase, mixed with the blow-by vapors and then passed through a crankcase ventilation valve and into the intake manifold. The primary component in the positive crankcase ventilation (PCV) system is the PCV valve, the valve meters the flow of blow-by vapors at a certain rate depending on manifold vacuum. To maintain idle quality, the PCV valve restricts the vapor flow when manifold vacuum is high. If abnormal operating conditions arise, the PCV system is designed to allow excessive amounts of blow-by vapors to back flow through the crankcase vent tube and into the engine air inlet to be consumed be normal combustion. The engine ventilation system was developed to minimize oil consumption and ensure that oil ingestion could not occur during vehicle limit handling maneuvers.

On the LS1 engine, filtered fresh air is routed from up stream of the throttle blade to the front of the right valve rocker arm cover through a formed rubber hose. To reduce the potential of oil pullover into the throttle bore area due to back flow of the ventilation system; the fitting in the right side rocker cover is shielded from the rocker arms and their oil spray. Blow-by vapors are routed from the rear of both rocker covers, through molded nylon lines to a tee fitting located on the centerline of the engine at the rear of the intake manifold. From there, a single nylon line carries the vapors through an externally mounted, horizontal PCV valve and enters the intake manifold behind the throttle body.

The dual draw PCV system was developed to meet the limited handling maneuver requirements. During sustained passively lateral accelerations, the outboard cover may fill with oil. The dual draw system passively switches, allowing the PCV valve to draw on the rocker cover with the least resistance. This results in the system drawing on the air filled, or inboard rocker cover and eliminates oil pullover due to drawing on the oil filled outboard rocker cover.

The PCV valve is connected to the PCV valve pipe. The PCV valve pipe is attached to the coolant air bleed pipe by a cable with an integral fastener. This cable transfers heat to the PCV valve to eliminate condensation build-up in the PCV system. This also aids in eliminating throttle body icing.

The LS6 engine utilizes an integral PCV system. The PCV system is moved into the engine's valley. The valley cover has composite oil separating baffles and PCV plumbing incorporated. The filtered fresh air is routed from up stream of the throttle blade to the front of the right valve rocker arm cover through a formed rubber hose. To reduce the potential of oil pullover into the throttle bore area due to back flow of the ventilation system; the fitting in the right side rocker cover is shielded from the rocker arms and their oil spray. Blow-by vapors are routed from the valley cover, through a formed rubber hose that carries the vapors through an externally mounted, horizontal PCV valve and enters the intake manifold behind the throttle body.