GM Chevy Mid-Size Cars 1964-1988 Repair Guide

Intake Manifold

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REMOVAL & INSTALLATION



See Figures 1, 2 and 3

Inline 6-Cylinder With Combination Manifold

Most the inline 6-cylinder engines covered in this guide are equipped with a combination intake/exhaust manifold. Once this combination manifold is removed from the vehicle, the fasteners may be removed and the 2 pieces separated. Certain late-model versions of the inline 250 engine are equipped with an integral intake in which the intake was actually part of the cylinder head. For these engines, which were used in the mid to late 1970's refer to the cylinder head procedure for removal of the integral intake and cylinder head. If your vehicle is equipped with a 250 engine, determine if it has an integral or combination intake by looking for intake manifold mounting bolts and/or a gasket seam between the cylinder head and the intake. If either are found, you have a combination manifold.

  1. Disconnect the negative battery cable, then remove the air cleaner assembly.
  2.  
  3. Disconnect the throttle rods at the bellcrank 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 straightedge and the manifold, distortion of that amount is present.
  14.  
  15. If necessary for replacement or service separate the manifold by removing one bolt and two nuts.
  16.  

To install:
  1. If separated, assemble the manifold and tighten the retainers.
  2.  
  3. Install the intake manifold using a new gasket, then carefully tighten the retainers.
  4.  
  5. Connect the exhaust pipe to the manifold.
  6.  
  7. Connect the evaporation control hose to the carbon canister and the crankcase ventilation hose to the valve cover.
  8.  
  9. Connect the fuel and vacuum lines to the carburetor.
  10.  
  11. Connect the throttle rods to the bellcrank and remove the throttle return spring.
  12.  
  13. Install the air cleaner assembly, then connect the negative battery cable.
  14.  
  15. Start and run the engine, then check for leaks.
  16.  



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Fig. Fig. 1: With the retainers, lines and wiring removed, the intake manifold may be lifted from the engine with most of it's mounted components attached



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Fig. Fig. 2: Remove the old manifold gaskets and clean the mating surfaces thoroughly before installation



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Fig. Fig. 3: Exploded view of a common gasoline V6 or V8 intake manifold assembly

Gasoline V6 and V8 (Except 231 V6)

See Figures 4, 5, 6 and 7

  1. Disconnect the negative battery cable, then remove the air cleaner assembly.
  2.  
  3. Drain the radiator to a level below the intake manifold.
  4.  


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

  1. Disconnect:
    1. Battery cables at the battery.
    2.  
    3. Upper radiator and heater hoses at the manifold.
    4.  
    5. Crankcase ventilation hoses as required.
    6.  
    7. Fuel line at the carburetor (V8) or the fuel line clips and lines at the throttle body (if equipped with TBI V6).
    8.  
    9. Accelerator linkage and TV cables (if equipped).
    10.  
    11. Vacuum hose at the distributor (if equipped).
    12.  
    13. Power brake hose at the carburetor base or manifold, if applicable.
    14.  
    15. Ignition coil, the spark plug wires and temperature sending switch wires.
    16.  
    17. Water pump bypass at the water pump (Mark IV only).
    18.  
    19. If equipped with CCC (V8), disconnect the electrical harness and lay it aside.
    20.  

  2.  
  3. Remove the distributor cap and scribe the rotor position relative to the distributor body.
  4.  
  5. Remove the distributor assembly from the engine.
  6.  
  7. If applicable, remove the alternator upper bracket. As required, remove the oil filler bracket, air cleaner bracket, air conditioning compressor and bracket, and accelerator bellcrank.
  8.  
  9. Remove the manifold-to-head attaching bolts, then remove the manifold and carburetor or throttle body as an assembly.
  10.  
  11. Using a putty knife clean the gasket and seal surfaces of the cylinder heads and manifold.
  12.  

To install:
  1. If the manifold is to be replaced, transfer the carburetor (and mounting studs), water outlet and thermostat (use a new gasket) heater hose adapter, EGR valve (use new gasket) and, if applicable, TVS switch and the choke coil. 1975-79 engines use a new carburetor heat choke tube which must be transferred to a new manifold.
  2.  
  3. Install the new manifold end seals, folding the tabs if applicable, and the manifold/head gaskets, using a sealing compound around the water passages.
  4.  

1974-75 V8 engines require a new intake manifold side gasket on 4-bbl engines. The new gasket has restricted crossover ports. The 350 2-bbl uses a restricted crossover gasket on the right hand side and an open gasket on the left. The 350 4-bbl uses restricted crossover gaskets on both sides. The correct gaskets are essential.

  1. Install the intake manifold assembly, taking care not to dislocate the end seals. It is helpful to use a pilot in the distributor opening. Tighten the manifold bolts to 30-35 ft. lbs. (41-47 Nm) in the proper torque sequence.
  2.  
  3. If applicable, install the alternator upper bracket. As required, install the oil filler bracket, air cleaner bracket, air conditioning compressor and bracket, and accelerator bellcrank.
  4.  
  5. Align the matchmarks made earlier and install the distributor to the engine making sure the rotor is facing the last of the matchmarks when the distributor housing is fully installed.
  6.  
  7. Connect all hoses, cables and wires which were disconnected for intake manifold removal.
  8.  
  9. Connect the negative battery cable, then properly refill the engine cooling system.
  10.  
  11. Start and run the engine, then check for leaks.
  12.  
  13. Check and adjust the timing, as necessary.
  14.  



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Fig. Fig. 4: V6 intake manifold and seal location (most V8 gasoline engines similar)



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Fig. Fig. 5: Intake manifold torque sequence-229 V6 and small block V8 engines



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Fig. Fig. 6: Intake manifold torque sequence-big-block V8 engine



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Fig. Fig. 7: Intake manifold torque sequence-262 V6 engine

231 V6

See Figure 8

A special wrench adapter, available from several tool manufacturers, is necessary to remove the left front intake manifold bolt.

  1. Disconnect the negative battery cable, then drain the engine cooling system.
  2.  


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

  1. Remove the upper radiator hose and the coolant bypass hose from the manifold.
  2.  
  3. Remove the air cleaner assembly. Disconnect the throttle linkage from the carburetor. If necessary, 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 a special fastener, known as a Torx® bolt. Remove the plug wires from the plugs.
  8.  



Click image to see an enlarged view

Fig. Fig. 8: Intake manifold torque sequence-231 V6 engine

  1. Remove the manifold.
  2.  
  3. Thoroughly clean the gasket mating surfaces on the engine and the intake manifold.
  4.  

To install:
  1. Position new gaskets and seals on the engine. 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.
  2.  
  3. 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.
  4.  
  5. Connect the anti-dieseling solenoid wire, the choke pipe and all vacuum lines.
  6.  
  7. If equipped with power brakes, connect the line to the manifold.
  8.  
  9. Connect the fuel line to the carburetor, then if removed, secure the linkage bracket to the manifold.
  10.  
  11. If equipped with an automatic transmission, connect the downshift linkage to the carburetor.
  12.  
  13. Connect the throttle linkage to the carburetor.
  14.  
  15. Install the air cleaner assembly, then connect the upper radiator hose and coolant bypass hose to the intake.
  16.  
  17. Connect the negative battery cable, then properly refill the engine cooling system.
  18.  
  19. Start and run the engine, then check for leaks.
  20.  

V6 and V8 Diesel

See Figures 9, 10 and 11

  1. Disconnect the negative battery cable, then remove the air cleaner assembly.
  2.  
  3. Drain the radiator and loosen the upper bypass hose clamp. Remove the thermostat housing bolts, the housing and the thermostat from the intake manifold.
  4.  


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

  1. Remove the breather pipes from the rocker covers and the air crossover. Remove the air crossover.
  2.  
  3. Disconnect the throttle rod and the return spring. If equipped with Cruise Control, remove the servo.
  4.  
  5. Remove the hairpin clip at the bellcrank and disconnect the cables. Remove the throttle cable from the bracket on the manifold; position the cable away from the engine. Disconnect and label any wiring as necessary.
  6.  
  7. If necessary, remove the alternator bracket. If equipped with air conditioning, remove the compressor mounting bolts and move the compressor aside, without disconnecting any of the hoses. Remove the compressor mounting bracket from the intake manifold.
  8.  
  9. Disconnect the fuel line from the pump and the fuel filter. Remove the fuel filter and bracket.
  10.  
  11. Remove the fuel injection pump and lines. Refer to Fuel System , Fuel System, for details and procedures.
  12.  
  13. Disconnect and remove the vacuum pump or oil pump drive assembly from the rear of the engine.
  14.  
  15. Remove the intake manifold drain tube.
  16.  
  17. Remove the intake manifold bolts and the manifold. Remove the adapter seal and the injection pump adapter.
  18.  
  19. Clean the mating surfaces of the cylinder heads and the intake manifold using a putting knife.
  20.  



Click image to see an enlarged view

Fig. Fig. 9: Exploded view of a diesel intake manifold and gaskets



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Fig. Fig. 10: V8 diesel intake manifold bolt torque sequence



Click image to see an enlarged view

Fig. Fig. 11: V6 diesel intake manifold bolt torque sequence

To install:
  1. For the V8 engine, coat both sides of the gasket surface that seal the intake manifold to the cylinder heads with G.M. sealer # 1050026 or the equivalent.
  2.  
  3. For the V6 engine, DO NOT coat the gasket or sealing surfaces with any sealer. Use an RTV sealer only on the end seals.
  4.  
  5. Position the intake manifold gaskets on the cylinder heads. Install the end seals, making sure that the ends are positioned under the cylinder heads.
  6.  
  7. Carefully lower the intake manifold into place on the engine.
  8.  
  9. Clean the intake manifold bolts thoroughly, then dip them in clean engine oil. Install the bolts and tighten to 15 ft. lbs. (20 Nm) in the sequence shown. In a second pass of the sequence, tighten all the bolts to 30 ft. lbs. (41 Nm). Finally, in a third pass of the sequence, tighten the bolts to 40 ft. lbs. (54 Nm).
  10.  
  11. Install the intake manifold drain tube and clamp.
  12.  
  13. Install injection pump adapter. Refer to Fuel System of this guide for details. If a new adapter is not being used, be sure to skip the steps for preparing a new adapter, as noted.
  14.  
  15. Install and connect the vacuum pump or oil pump drive assembly from the rear of the engine.
  16.  
  17. Install the fuel injection pump and lines.
  18.  
  19. Install the fuel filter and bracket, then connect the fuel line to the pump and filter.
  20.  
  21. If equipped with A/C, install the compressor bracket to the intake manifold, then reposition and secure the compressor assembly.
  22.  
  23. If removed, install the alternator bracket.
  24.  
  25. Connect the wiring as tagged during removal.
  26.  
  27. Connect the throttle cable and secure it in the bracket. Connect the cables and install the hairpin clip at the bellcrank.
  28.  
  29. If equipped with Cruise Control, install the servo.
  30.  
  31. Connect the throttle rod and return spring.
  32.  
  33. Install the air crossover, then connect the breather pipes to the rocker covers and the crossover.
  34.  
  35. Install the thermostat housing and tighten the retaining bolts, then connect and tighten the upper bypass hose clamp.
  36.  
  37. Connect the negative battery cable and properly refill the engine cooling system.
  38.  
  39. Start and run the engine, then check for leaks.
  40.  

 
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