GM Corvette 1963-1982 Repair Guide

Distributor

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REMOVAL - Conventional and Transistorized Systems



See Figures 1 through 5

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Fig. Fig. 1: Exploded view of the conventional V8 engine point-type distributor



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Fig. Fig. 2: Mark the position of the rotor on the distributor, then mark the distributor to the manifold



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Fig. Fig. 3: Distributor wrenches are available to loosen the hold-down bolt



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Fig. Fig. 4: Remove the distributor hold-down clamp



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Fig. Fig. 5: Carefully pull the distributor from the engine. Do NOT rotate the engine while the distributor is removed

  1. Rotate the engine until the timing mark on the crankshaft balancer is aligned with the top dead center mark (TDC or "0") on the timing tab scale. Remove the air cleaner assembly.
  2.  
  3. Remove the ignition shielding and disconnect the secondary (high tension) coil wire.
  4.  
  5. Release the distributor cap hold-down screws (push down and turn counterclockwise). Raise the distributor cap off of the distributor and check that the firing tip of the rotor is pointed at the #1 terminal of the distributor cap. If it is not; turn the engine one full revolution and again align the timing marks as previously stated. Recheck the rotor position.
  6.  
  7. Pull the plug wires out of the locating looms (if so equipped) and move the cap out of the way. Leave the plug wires attached to the cap.
  8.  
  9. Disconnect the battery cables at the battery.
  10.  
  11. Disconnect the tachometer and fuel injection drive cables from the distributor, if so equipped.
  12.  
  13. Disconnect the vacuum line from the distributor vacuum advance unit, if so equipped.
  14.  
  15. Mark the relationships between the following items:
  16.  

  1. Rotor firing tip and distributor body.
  2.  
  3. Distributor body and either the firewall or the intake manifold.
  4.  

The combination of these marks will assure that the distributor gear is properly meshed with the camshaft and the ignition timing will be close enough to start the engine after the distributor is reinstalled.

  1. On conventional ignitions, disconnect the distributor lead from the negative (-) terminal of the ignition coil. On transistorized systems, carefully release and pull apart the quick-disconnect of the two-wire distributor lead.
  2.  
  3. Remove the distributor hold-down bolt and plate.
  4.  
  5. Carefully pull the distributor from the engine. Note the rotation of the rotor as the distributor is pulled upward, caused by the angled distributor drive teeth.
  6.  


CAUTION
Do not rotate the engine while the distributor is removed.

  1. Service the distributor as necessary.
  2.  

H.E.I. Systems See Figure 6

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Fig. Fig. 6: Exploded view of the HEI distributor. Note that engines with the computer emissions system do not have the vacuum advance unit

  1. Rotate the engine until the timing mark on the balancer is aligned with the top dead center mark (TDC or "O") on the timing tab scale.
  2.  
  3. Remove the air cleaner assembly and the ignition shielding.
  4.  
  5. With the ignition switch OFF, disconnect the feed, module, and tachometer wiring from the drivers side of the distributor cap. Do so by releasing the connector retaining tabs and pulling downward on the connectors. On 1981-82 models, also disconnect the four-wire connector installed in the wiring from the opposite side of the distributor.
  6.  


CAUTION
Never allow the "Tach" terminal to touch ground.

  1. Locate the locking tabs of the spark plug wire retaining ring (on the distributor cap). Move each of the two locking tabs outward to release the retaining ring. With the plug wires still attached to the ring, carefully remove the retaining ring from the distributor cap. Pull the plug wires out of the locating looms (if so equipped) and move the ring (with the wires still attached) out of the way.
  2.  
  3. Release the distributor cap hold-down screws (push downward and turn counterclockwise) and lift the cap assembly off of the distributor. Check that the firing tip of the rotor is pointed at the #1 terminal of the distributor cap; if it is not, rotate the engine one full revolution and again align the timing marks. Recheck the position of the rotor.
  4.  
  5. Disconnect the vacuum line from the distributor vacuum advance unit, if so equipped.
  6.  
  7. Follow steps 5, 7, 8, and 10-12 of the previous procedure, in that order to complete distributor removal.
  8.  

INSTALLATION - Engine Not Disturbed



  1. Clean the distributor and intake manifold mating surfaces and check the condition of the cork gasket. Replace the gasket if it is damaged.
  2.  
  3. Position the distributor in the engine without yet engaging it. Align the distributor housing-to-engine alignment marks which were made during removal. Position the rotor firing tip slightly counterclockwise of the corresponding distributor housing mark; remember, the rotor will turn slightly during installation.
  4.  
  5. Engage the distributor to the engine by moving it downward. The rotor should turn to its proper alignment position. If it does not, lift the distributor enough to disengage the drive gear, reposition the rotor and lower the distributor.
  6.  
  7. Install the distributor hold-down plate and just snug down the bolt.
  8.  
  9. Make sure that the rotor retaining screws are tight and install the distributor cap.
  10.  
  11. Connect the cables (tach, injection-if so equipped), wires, and vacuum line (if so equipped) to the distributor.
  12.  
  13. On conventional ignitions, reconnect the primary distributor lead to the coil. On models without H.E.I., reconnect the secondary coil wire.
  14.  
  15. On H.E.I. models, install the plug wire retaining ring. Press the ring downward until the two locking tabs engage. Make sure that the plug wire terminals are firmly seated on the distributor cap terminals.
  16.  
  17. Reposition the plug wires into their locating looms, if so equipped.
  18.  
  19. Install the air cleaner and reconnect the battery cables.
  20.  
  21. Adjust the ignition timing as previously outlined and tighten the distributor hold-down bolt. Reinstall the ignition shielding as necessary.
  22.  

Engine Disturbed

  1. The piston of the #1 cylinder must be on its compression stroke and at the top of its travel (top dead center-TDC) in order to time the ignition system to the engine. There are several ways to determine when the piston is on its compression stroke. In any case, the #1 spark plug must be removed. The various methods are as follows:
  2.  

  1. Hold your finger over the spark plug hole and have an assistant turn the engine over slowly. When you feel compression, watch the timing marks. Stop turning the engine over as soon as the timing mark on the crankshaft balancer is aligned with the "0" mark on the timing tab scale.
  2.  
  3. Insert a rag into the spark plug hole (NOT into the cylinder). Turn the engine over slowly until the rag is blown out of the hole. Stop cranking the engine when this happens and check the timing marks. If necessary, "tap" the ignition key until the timing mark on the crankshaft balancer is aligned with the "0" mark on the timing tab scale.
  4.  
  5. Attach a compression gauge to the spark plug hole (preferably the screw-in type; eliminating the need for an assistant). Position the gauge dial so that it may be viewed while cranking the engine. Turn the engine over until the gauge needle reading increases, indicating compression. Stop cranking the engine when this happens and check the timing marks. If necessary, "tap" the ignition key until the timing mark on the crankshaft balancer is aligned with the "0" mark on the timing tab scale. Remove the compression gauge.
  6.  

There are tools available commercially which screw into the #1 spark plug hole and register (more accurately than the above methods) when top dead center is reached. If one of these tools is used, follow the tool manufacturers instructions.

  1. Reinstall the #1 spark plug and connect the plug wire. With the distributor out of the vehicle and the distributor cap installed, locate the #1 distributor cap terminal and chalk mark its position on the distributor housing. Remove the distributor cap.
  2.  
  3. Position the distributor into the engine block with the:
  4.  

  1. vacuum advance unit in its proper position (see the Firing Order illustrations).
  2.  
  3. firing tip of the rotor pointing to the mark made during step 2.
  4.  

  1. As the distributor drive gear engages, the rotor will turn slightly. If the distributor housing does not sit properly on the block, the oil pump shaft is not engaging with the distributor shaft. In this case, you can do one of two things:
  2.  

  1. Remove the distributor and turn the oil pump driveshaft with a long screwdriver to align the pump driveshaft slot with the "blade" of the distributor shaft. This is done strictly by visual approximation.
  2.  
  3. Apply downward pressure on the distributor housing (NOT the rotor) and have someone "tap" the ignition key to slowly turn the engine over until the distributor falls into its proper position. After doing this, it is recommended that you recheck the timing by repeating steps 1 and 2.
  4.  

  1. On conventional ignitions, after proper positioning is assured, turn the distributor housing so that the points are just opening.
  2.  
  3. Install the distributor hold-down bolt and plate. Snug down the retaining bolt.
  4.  
  5. Connect the vacuum advance hose, tach drive cable, and injection drive cable, on vehicles equipped with these items.
  6.  
  7. Connect all wiring and adjust the ignition timing as previously outlined.
  8.  
  9. Install the ignition shielding.
  10.  

DISASSEMBLY - HEI DISTRIBUTOR



See Figure 7

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Fig. Fig. 7: HEI DISTRIBUTOR

  1. Distributor Cap
  2.  
  3. Distributor Cap Cover
  4.  
  5. Ignition Coil
  6.  
  7. Washer
  8.  
  9. Rotor
  10.  
  11. Advance Weights
  12.  
  13. Distributor Mainshaft
  14.  
  15. Ignition Module
  16.  
  17. Capacitor
  18.  
  19. Pole Piece
  20.  
  21. Distributor Housing
  22.  
  23. Distributor Driven Gear
  24.  
  25. Tang Under Gear Washer
  26.  
  27. Under Gear Washer
  28.  
  29. Pickup Coil
  30.  
  31. Vacuum Advance Unit
  32.  

Conventional Systems

  1. Remove the distributor cap and the rotor.
  2.  
  3. Remove the two-piece radio interference shield (2 fasteners), if so equipped.
  4.  
  5. Remove the centrifugal advance springs and weights.
  6.  
  7. Drive the roll pin out of the distributor gear using a drift no larger than the roll pin.
  8.  
  9. Slide the distributor gear off of the shaft and remove the spacers and washers (note their arrangement for reinstallation).
  10.  
  11. Remove the tachometer drive gear.
  12.  
  13. Inspect the distributor shaft for burrs in the gear mounting area. If there are any burrs or nicks, carefully smooth them with a fine file. This should be done to prevent bushing damage as the distributor shaft is withdrawn from the housing.
  14.  
  15. Slide the distributor shaft assembly out of the housing.
  16.  
  17. Remove the vacuum advance unit (2 screws).
  18.  
  19. Carefully remove the breaker plate retaining ring and lift the breaker plate off of the distributor housing. DO NOT disassemble the breaker plate any further.
  20.  
  21. Remove the point set, condenser, and the condenser mounting bracket from the breaker plate. Remove the washer and seal from beneath the breaker plate.
  22.  

Transistorized Systems

  1. Remove the distributor cap and the rotor.
  2.  
  3. Remove the centrifugal advance springs and weights.
  4.  
  5. Remove the tachometer drive gear.
  6.  
  7. Support the distributor gear (to prevent damage to the magnetic pickup assembly) and drive the roll pin out of the gear, using a drift no larger than the roll pin.
  8.  
  9. Slide the distributor gear and washer off of the distributor shaft.
  10.  
  11. Inspect the distributor shaft for burrs in the gear mounting area. If there are any burrs or nicks, carefully smooth them with a fine file. This should be done to prevent bushing damage as the distributor shaft is withdrawn from the housing.
  12.  
  13. Remove the centrifugal advance weight support and timer core from the distributor shaft.
  14.  
  15. Disconnect the pickup coil lead connector.
  16.  
  17. Remove the retaining ring which secures the magnetic pickup assembly to the distributor housing.
  18.  
  19. Remove the entire magnetic pickup assembly from the distributor housing. DO NOT remove the three screws which secure the stationary pole piece to the pickup assembly.
  20.  
  21. Remove the washer and felt pad from the pickup mounting.
  22.  
  23. Remove the vacuum advance unit.
  24.  

H.E.I. Systems

  1. Remove the distributor cap assembly and rotor as previously outlined.
  2.  
  3. Remove the centrifugal advance springs and weights from the mainshaft, if so equipped.
  4.  
  5. Drive out the distributor gear roll pin using a drift.
  6.  
  7. Remove the distributor gear and washers. Note the location of the washers so that they may be reinstalled properly.
  8.  
  9. Slide the distributor shaft out of the housing.
  10.  
  11. Disconnect the electrical leads from the module and remove the module. Also remove the capacitor.
  12.  
  13. If the internal teeth of the pickup assembly are fully exposed; remove the pickup retaining ring and remove the pickup assembly from the distributor housing (Do not remove the three screws from the pickup assembly). If the internal teeth of the pickup are not fully exposed; remove the magnetic shield from the pickup assembly (three attaching screws). Remove the pickup assembly retaining ring and remove the pickup components (magnet, pole piece, pickup coil).
  14.  
  15. Remove the vacuum advance unit, if so equipped.
  16.  

ASSEMBLY



Assembly of the distributor is the reverse of its respective disassembly procedure.

When assembling the distributor, be sure to lubricate the distributor shaft bushings with a few drops of engine oil. Also be sure that the distributor shaft turns freely after it is installed. On conventional, point-type distributors, it is easier to install and gap the points while the distributor is removed.

On H.E.I. systems, apply a light coating of silicone dielectric compound to the distributor housing in the module mounting area before installing the module. The silicone compound is used to transfer heat from the module to the distributor housing. If the compound is not used, the module will overheat, causing failure of the ignition system.

Silicone compounds are available strictly for this purpose-DO NOT use a regular silicone lubricant or sealer.

Refer to the previous middle replacement procedure for additional module installation information.

 
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