GM Firebird 1967-1981 Repair Guide

Intake Manifold

Print

REMOVAL & INSTALLATION 230 and 250 Engines



1975 and later L6 engines are equipped with an intake manifold which is integral with the cylinder head.

  1. Remove the air cleaner.
  2.  
  3. Disconnect the throttle rods at the bell crank and remove the throttle return spring.
  4.  
  5. Disconnect the fuel and vacuum lines from the carburetor.
  6.  
  7. Disconnect the crankcase ventilation hose from the valve cover and the evaporation control hose from the carbon canister.
  8.  
  9. Disconnect the exhaust pipe from the manifold and throw away the packing.
  10.  
  11. Remove the manifold assembly and scrape off the gaskets.
  12.  
  13. Check the condition of the manifold. If a manifold is cracked or distorted 0.030 in. or more, it should be replaced to prevent exhaust leakage. To detect distortion, lay a straightedge along the length of the exhaust port faces. If, at any point, a gap of 0.030 in. or more exists between the straight edge and the manifold, distortion of that amount is present.
  14.  
  15. By removing one bolt and two nuts, the manifold can be separated.
  16.  
  17. To install, reverse the removal procedure, using new gaskets. Replace the exhaust pipe packing.
  18.  

265, 301, 305, 326, 350, 400, 403 and 455 Engines See Figures 1 through 14

Click image to see an enlarged view

Fig. Fig. 1: The intake manifold gasket on Pontiac 8-cylinder engines can be held in place by plastic retainers



Click image to see an enlarged view

Fig. Fig. 2: When tightening the intake manifold bolts on 403 and 1977 350 (Oldsmobile) engines, make certain to adhere to the sequence shown



Click image to see an enlarged view

Fig. Fig. 3: Make certain to tighten the intake manifold bolts in the sequence shown 305 and 1978-79 350 (Chevrolet) engines



Click image to see an enlarged view

Fig. Fig. 4: Exploded view of the 403 and 1977 350 (Oldsmobile) intake manifold and related components



Click image to see an enlarged view

Fig. Fig. 5: To remove the intake manifold, first label and detach all vacuum lines ...



Click image to see an enlarged view

Fig. Fig. 6: ... then detach all coolant hoses from the manifold



Click image to see an enlarged view

Fig. Fig. 7: Detach the linkage from the carburetor, then remove the linkage bracket mounting bolts ...



Click image to see an enlarged view

Fig. Fig. 8: ... and position the linkage/bracket assembly out of the way



Click image to see an enlarged view

Fig. Fig. 9: Remove any bracket bolts and all intake manifold retaining bolts ...



Click image to see an enlarged view

Fig. Fig. 10: ... then lift the manifold off of the engine 305 shown, others similar



Click image to see an enlarged view

Fig. Fig. 11: Once the intake manifold is removed the lifter valley can be accessed



Click image to see an enlarged view

Fig. Fig. 12: Push towels or rags into the cylinder head holes ...



Click image to see an enlarged view

Fig. Fig. 13: ... then clean all old gasket material from the cylinder heads



Click image to see an enlarged view

Fig. Fig. 14: To remove the exhaust manifold, first bend back the bolt retainers ...

Remove the EGR valve on all 1973 and later engines (except the 301).


CAUTION
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 the cooling system.
  2.  
  3. Remove the air cleaner assembly.
  4.  
  5. Remove the water outlet fitting allowing the radiator hose to remain attached.
  6.  
  7. As necessary, disconnect the heater hose from its fitting.
  8.  
  9. Disconnect the wire from the temperature gauge sending unit.
  10.  
  11. Remove the spark plug wire bracket.
  12.  
  13. If equipped with power brakes, remove the vacuum pipe from the carburetor.
  14.  
  15. Disconnect the fuel line and the vacuum hoses.
  16.  
  17. Disconnect the crankcase vent hose from the manifold.
  18.  
  19. Disconnect the throttle linkage from the carburetor.
  20.  

If your car is equipped with the 301 V8 (TURBO), before proceeding any further you must remove the turbocharger and actuator assembly as detailed later in this section.

  1. Remove the screws from the throttle control bracket.
  2.  
  3. Remove the manifold bolts and lift off the manifold.
  4.  

It may be necessary to remove the distributor for clearance.

  1. Install new gaskets on the cylinder heads keeping them in position with plastic gasket retainers (Pontiac-built engines only).
  2.  
  3. Lower the intake manifold onto the engine and install the O-ring seal.
  4.  
  5. Loosely install the bolts and nuts.
  6.  
  7. Install the throttle control bracket assembly.
  8.  
  9. Install a new O-ring seal (use the old one if undamaged) between the timing chain cover and the intake manifold and tighten the bolt to 15 ft. lbs.
  10.  
  11. Tighten all bolts and nuts evenly to 40 ft. lbs., starting from the center and working out.
  12.  
  13. To complete the installation, reverse the removal procedures.
  14.  

231 V6 Engine See Figure 15

Click image to see an enlarged view

Fig. Fig. 15: Tighten the 231 V6 engine intake manifold mounting bolts in the sequence shown

A Torx socket will be necessary to remove the left front intake manifold bolt.


CAUTION
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. Disconnect the battery and drain the cooling system. Remove the upper radiator hose, and the coolant bypass hose from the manifold.
  2.  
  3. Remove the air cleaner. Disconnect the throttle linkage from the carburetor. Remove the linkage bracket from the manifold. If the car is equipped with an automatic transmission, remove the downshift linkage.
  4.  
  5. Disconnect the fuel line from the carburetor. If equipped with power brakes, disconnect the power brake line from the manifold. Disconnect the choke pipe and all vacuum lines. Disconnect the anti-dieseling solenoid wire.
  6.  
  7. Remove the manifold bolts. It will be necessary to remove the distributor cap and rotor to gain access to the front left manifold bolt. This is the torx bolt. Remove the plug wires from the plugs.
  8.  
  9. Remove the manifold.
  10.  
  11. Installation is in the reverse order of removal. Use a new gasket and seals. Coat the ends of the seals with a non-hardening silicone sealer. The pointed end of the seal should be a snug fit against the block and head. When installing the manifold, start with the center bolts (numbers one and two) and slowly tighten them until snug. Continue with the rest of the bolts in sequence, tightening them in several stages to the correct torque.
  12.  

 
label.common.footer.alt.autozoneLogo