REMOVAL & INSTALLATION
- Remove the distributor cap and position it out of the way.
- Disconnect the primary coil wire and the vacuum advance hose.
- Scribe a mark on the distributor body and the engine block showing their relationship. Mark the distributor housing to show the direction in which the rotor is pointing. Note the positioning of the vacuum advance unit.
- Remove the hold-down bolt and clamp and remove the distributor.
- Reinsert the distributor into its opening, aligning the previously made marks on the housing and the engine block.
- The rotor may have to be turned either way a slight amount to align the rotor-to-housing marks.
- Install the retaining clamp and bolt. Install the distributor cap, primary wire or electrical connector, and the vacuum hose.
- Start the engine and check the ignition timing.
To install the distributor with the engine disturbed:
- Turn the engine to bring No. 1 piston to the top of its compression stroke. This may be determined by placing your finger over the No. 1 spark plug hole and slowly turning the engine over. When the timing mark on the crankshaft pulley aligns with the 0 on the timing scale you will feel pressure against your finger. This is when the No. 1 cylinder is on the compression stroke.
On some 400 and 455 V8 engines there is a punch mark on the distributor drive gear which indicates the rotor position. Thus, the distributor may be installed with the cap in place. Align the punch mark 2° clockwise from the No. 1 cap terminal, then rotate the distributor body 1 / 8 turn counterclockwise and push the distributor down into the block.
- Install the distributor in the engine block so that the vacuum advance unit points in the correct direction.
- Turn the rotor so that it will point to No. 1 terminal in the cap. It may be necessary to turn the rotor a little in either direction in order to engage the gears.
- Tap the starter a few times to ensure that the oil pump shaft is mated to the distributor shaft.
- Bring the engine to No. 1 TDC again and check to see that the rotor is indeed pointing toward the No. 1 terminal of the cap.
- After correct positioning is assured, turn the distributor housing so that the points are just opening. Tighten the retaining clamp.
- Install the cap and primary wire. Check the ignition timing. Install the vacuum hose.
The Delco-Remy Energy Ignition (HEI) System is a breakerless, pulse triggered, transistor controlled, inductive discharge ignition system available as an option in 1974 and standard in all Pontiacs beginning in 1975.
There are only nine electrical connections in the system; the ignition switch feed wire and the eight spark plug leads. On all models, the ignition coil is located in the distributor cap, connecting directly to the rotor.
The magnetic pick up assembly located inside the distributor contains a permanent magnet, a pole piece with internal teeth, and a pick up coil. When the teeth of the rotating timer core and pole piece align, an induced voltage in the pick-up coil signals the electronic module to open the coil primary circuit. As the primary current decreases, a high voltage is induced in the secondary windings of the ignition coil directing a spark through the rotor and high voltage leads to fire the spark plugs. The dwell period is automatically controlled by the electronic module and is increased with increasing engine rpm. The HEI system features, as do most electronic ignition systems, a longer spark duration which is instrumental in firing today's lean and EGR-diluted fuel/air mixtures (a lean mixture requires a much hotter, longer duration spark to ignite it than does a rich mixture). A capacitor, which looks like the condenser in the old points-type ignition systems, is located within the HEI distributor and is used for noise (static) suppression in conjunction with the car's radio. The capacitor is not a regularly replaced component.
As noted in , 1981 and later models continue to use the HEI distributor, although it now incorporates an Electronic Spark Timing system (for more information on EST, please refer to ). With the EST system, all spark timing changes are performed electronically by the Electronic Control Module (ECM) which monitors information from various engine sensors, computes the desired spark timing and then signals the distributor to change the timing accordingly. Because all timing changes are controlled electronically, no vacuum or mechanical advance systems are used.
- Disconnect the ground cable from the battery.
- Tag and disconnect the feed and module terminal connectors from the distributor cap.
- On 1975-80 models, disconnect the hose at the vacuum advance unit.
- Depress and release the 4 distributor cap-to-housing retainers and lift off the cap assembly.
- Using a magic marker, make locating marks on the rotor and module and on the distributor housing and engine to simplify installation.
The distributor must be installed with the rotor in the correct position.
- Loosen and remove the distributor clamp bolt and clamp, and lift the distributor out of the engine. Noting the relative position of the rotor and module alignment marks, make a second mark on the rotor to align it with the mark on the module.
- With a new O-ring on the distributor housing and the second mark on the rotor aligned with the mark on the module, install the distributor, taking care to align the mark on the housing with the one on the engine. It may be necessary to lift the distributor and turn the rotor slightly to align the gears and the oil pump driveshaft.
- With the respective marks aligned, install the clamp and bolt finger-tight.
- Install and secure the distributor cap.
- Connect the feed and module connectors to the distributor cap.
- Connect a timing light to the engine and plug the vacuum hose.
- Connect the ground cable to the battery.
- Start the engine and set the timing.
- Turn the engine off and tighten the distributor clamp bolt. Disconnect the timing light and unplug and disconnect the hose to the vacuum advance.