The exhaust system on the L47 engine incorporates (in order from front to rear):

The exhaust crossover pipe is attached to the front and rear exhaust manifolds. A joint coupling, using a round graphite impregnated seal, connects the rear exhaust manifold pipe to the inlet of the catalytic converter. The rear exhaust manifold pipe contains a flex joint. The flex joint replaces the exhaust springs commonly used with bolts that attach the rear exhaust pipe to the manifold and crossover pipe. The intermediate pipe assembly is welded to the converter outlet.

The exhaust system on the L67 engine incorporates (in order from the front to the rear):

The exhaust manifold front pipe is welded to the catalytic converter therefore, they are serviced as one unit. The exhaust crossover pipe attaches to the front and the rear exhaust manifolds.

All exhaust pipe to exhaust manifold connections are of the ball joint type to allow angular movement for engine roll motion.

The catalytic converter is an emission control device added to the exhaust system on unleaded fuel gasoline engine vehicles to reduce pollutants from the exhaust gas stream. The catalyst in the monolith converter is serviced by replacement only. the converter is the single bed type.

Notice: In order to avoid damage to the catalyst, use unleaded fuel only.

The catalytic converter also contains a second oxygen sensor which is located near the outlet of the converter.

The Oldsmobile with a L47 engine and the Buick with the L67 engine use heat shields that are attached to the underside of the body. They are there to reflect the heat of the exhaust system away from the body.

Caution: Damage may occur to related components if a removed heatshield is not reinstalled.

The post catalytic converter oxygen sensor is protected by a heat shield which is attached to the underbody of the vehicle.

The exhaust systems are supported by free-hanging rubber mountings (2) which permit some movement of the exhaust system. The free-hanging rubber mountings do not permit transfer of noise and vibration into the passenger compartment.

Annoying rattles and noise vibrations in the exhaust system can be caused by misalignment of parts or retention of heat shields. When aligning the system, leave all of the bolts or nuts loose until all of the parts are properly aligned. Then, tighten them working from the front to the rear.

Tighten them working from the front to the rear.

Tighten them working from the front to the rear.

Notice: When jacking or lifting the vehicle from the frame side rails, be certain that the lift pads do not contact the catalytic converter. This may damage the converter.

Periodic maintenance of the exhaust system is not required; however, if the car is raised for other service, it is advisable to check the general condition of the catalytic converter, pipes, and mufflers.

Notice: If there is any mis-positioning, incorrect installation, or failure of components in the brake system pipes, hoses, or wheel cylinders, check for brake damage. The exhaust system components must have adequate clearance from the floor pan to avoid overheating of the floor pan, damage to the passenger compartment carpets and damage to items in the luggage compartments.

When installing exhaust parts, make sure there is enough clearance between the hot exhaust parts and the pipes and hoses. The pipes and hoses could be damaged by the heat.

Inspect the following components for damage:

Damage could include any of the following conditions:

These conditions could permit exhaust fumes to seep into the trunk or passenger compartment. Any damaged areas must be corrected immediately.

The exhaust system is welded and can be serviced by the following components:

Follow the below guidlines when servicing this system:

Exhaust system hangers minimize noise transfer through hangers. If the system contacts the body, or the hanger is restricted, vibration and noise can be transmitted into the vehicle.

Position the clamps and the insulators so that the hangers are vertical when the exhaust system is at operating temperature. The support brackets should be horizontal.

If the pipes need to be repositioned, heat may be used in front of rear suspension. The support brackets should be horizontal. Do not touch the pipes while they are hot. Do not use an acetylene torch neat the fuel tank.

After the hangers and/or the repositioning pipes have been adjusted, check the entire system for adequate clearance to frame members and floor plan, minimum 15 mm (5/8 inch). Tighten all of the clamps according to specified torque's. Clearance is needed to avoid possible damage to the passenger compartment carpets. Distribute the weight of the exhaust system evenly on all brackets and hangers as indicated by an equal deflection at each hanger.

Some vehicles may exhibit exhaust system misalignment due to an improper installation process of the front pipe (L67). When installed low in the assembly, the front pipe (L67) can pull the exhaust system forward and hit part of the body. The pipes being installed low in the assembly can also make the exhaust system close enough to the body that when the vehicle goes over a bump, it may contact the body. To properly correct the condition, reinstall the rear pipe based upon the on-vehicle service procedure. The exhaust system should move into proper alignment. Refer to Exhaust System Clearances .

Refer to Exhaust Crossover Replacement in Engine Mechanical for the on-vehicle service of the crossover pipe for the L47 and the L67.