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GM Firebird 1967-1981 Repair Guide



See Figure 1

Click image to see an enlarged view

Fig. Fig. 1: Exploded view of the turbocharger compressor housing and the turbine housing mounting

In 1980, turbocharging was added as an option for the 301 V8 engine. With this application, Pontiac was able to improve the performance of the 301 while at the same time maintaining the capability of good fuel economy. The 301 Turbo, although more complicated than its naturally-aspirated twin, continues to utilize most of the same design features.

A turbocharger is used to increase power whenever there is a demand for it. As the load on the engine is increased and the throttle is opened, more air/fuel mixture flows into the combustion chamber. As this increased flow is burned, a larger volume of higher energy exhaust gas enters the exhaust system and is then directed through the turbocharger turbine housing. Some of this extra energy is used to increase the speed of the turbine wheel. The turbine wheel is connected by means of a shaft to the compressor wheel. The increased speed of the compressor wheel allows it to compress the air/fuel mixture that it receives from the carburetor and delivers to the intake manifold. This resulting higher pressure in the intake manifold will allow a denser charge to enter the combustion chamber, the denser charge can then develop more power during the combustion cycle.

The intake manifold pressure (boost) is controlled to a factory-set maximum value by an exhaust bypass valve (wastegate). The valve allows a portion of the exhaust gases to bypass the turbine wheel, thus not increasing the turbine wheel past its maximum speed. The wastegate is operated by a spring loaded diaphragm device (actuator assembly) that senses the pressure differential across the compressor. When the boost reaches a preset value above the ambient pressure, the wastegate will begin to bypass the exhaust gases.


Before beginning any turbocharger disassembly procedures, the following general precautions should be considered.

Clean the area around the turbocharger with non-caustic solution before removal of the assembly.
When removing the turbocharger assembly, take special care not to bend, nick or in any way damage the compressor or turbine wheels. The turbine and compressor wheels routinely reach 130,000 rpm during boost, at which speeds the slightest imbalance can be destructive.
Before disconnecting the center housing rotating assembly from either compressor housing or turbine housing, scribe the components and make sure they are reassembled in the same order.
Any time the center housing rotating assembly or any part of the turbocharger assembly which includes the center housing assembly is being replaced, the oil and oil filter should be changed as part of the repair procedure.

REMOVAL & INSTALLATION Wastegate Activator Assembly

  1. Disconnect the two hoses from the actuator.
  3. Remove the waste gate linkage-to-actuator rod clip.
  5. Remove the two bolts attaching the actuator to the compressor housing.
  7. Installation is the reverse of removal.

Turbocharger and Actuator Assembly See Figure 2

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Fig. Fig. 2: The turbocharger mounts onto the plenum with 6 bolts the arrow indicates the actuator

The carburetor and plenum are removed as a unit with the turbocharger.

  1. Disconnect the turbocharger exhaust inlet and outlet pipes at the turbocharger. Remove the air cleaner.
  3. Disconnect all carburetor and transmission control linkages at the carburetor. Disconnect and plug the carburetor fuel line and necessary vacuum lines.

When draining engine coolant, keep in mind that cats and dogs are attracted to ethylene glycol antifreeze and could drink any that is left in an uncovered container or in puddles on the ground. This will prove fatal in sufficient quantity. Always drain coolant into a sealable container. Coolant should be reused unless it is contaminated or is several years old.

  1. Drain about 3 quarts of coolant from the radiator. Disconnect the coolant hoses from the front and rear of the plenum.
  3. Disconnect the EGR pipe at the intake manifold fitting. Remove the two bolts attaching the turbine housing to the bracket on the intake manifold.
  5. Remove the three bolts attaching the compressor housing to the intake manifold.
  7. Remove the turbocharger, actuator, carburetor and plenum as an assembly. Disconnect vacuum hoses as necessary.
  9. Remove the six bolts attaching the turbocharger to the carburetor/plenum to separate the components if necessary.