See Figures 1 and 2
A point type ignition was originally installed on all 1964-73 vehicles covered in this guide. Most 1974 vehicles were also equipped with a point type distributor, though some may be found with the HEI system option. HEI ignition systems are often substituted in repairs or maintenance on these vehicles. If your distributor does not contain points, refer to the HEI ignition system procedures later in this section for service information.
The points function as a circuit breaker for the primary circuit of the ignition system. The ignition coil must boost the 12 volts supplied by the vehicle's charging system to as much as 25,000 volts in order to fire the plugs. To accomplish, the coil depends on the points and the condenser to make a clean break in the primary circuit.
The coil has both primary and secondary circuits. When the ignition is turned on, the battery supplies voltage through the coil and to the points. The points are connected to ground, completing the primary circuit. As the current passes through the coil, a magnetic field is created in the iron center core of the coil. When the cam on the distributor shaft turns, the points open, breaking the primary circuit. The magnetic field in the primary circuit of the coil then collapses and cuts through the secondary circuit windings around the iron core. Because of the physical principle called electromagnetic induction, the voltage is increased to a level sufficient to fire the spark plugs.
When the points open, the electrical charge in the primary circuit tries to jump the gap created between the two open contacts of the points. If this electrical charge were not transferred elsewhere, the metal contacts of the points would start to charge rapidly. The function of the condenser is to absorb excessive voltage from the points when they open and thus prevent the points from becoming pitted or burned.
If you have ever wondered why it is necessary to tune-up your engine occasionally, consider the fact that the ignition system must complete the above cycle each time a spark plug fires. On a 4-cylinder, 4-cycle engine, two of the four plugs must fire once for every engine revolution. If the idle speed of you engine is 800 revolutions per minute (800 rpm), the breaker points open and close two times for each revolution. For every minute your engine idles, your points open and close 1,600 times (2 x 800 = 1,600). And that is just at idle. Just think at the work your points are performing at 60 mph and you will begin to realize why periodic engine tuning is so important.
There breaker point gap may be checked in either of 2 ways: with a feeler gauge or with a dwell meter. In both cases setting the points means that you are adjusting the amount of time (in degrees of distributor rotation) that the points will remain open. If you adjust the points with a feeler gauge, you are setting the maximum amount that points will open when the point rubbing block is on a high point of the distributor cam. When you adjust the points with a dwell meter, you are measuring the number of degrees (of distributor cam rotation) that the points will remain closed before they start to open as a high point of the distributor cam approaches the rubbing block of the points.
If you would like a demonstration of how the points function mechanically, take a friend, go outside, and remove the distributor cap from your engine. Make sure the parking brake is set and that the transmission is not in gear, then have your friend operate the starter for a few seconds as you look at the exposed parts of the distributor. Be sure to keep yourself and your clothing away from any moving engine parts for safety reasons. You should see the points open and close as the distributor rotates.
There are two rules that should always be followed when adjusting or replacing points. The points and condenser are normally replaced as a set; when replacing the points, the condenser should also be replaced. If you change the point gap or dwell of the engine, you will affect the ignition timing. Therefore, if you adjust the points, you must also adjust the timing.
REMOVAL & INSTALLATION
See Figures 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13 and 14
The usual procedure is to replace the condenser each time the point set is replaced. Although this is not always necessary, it is easy to do at this time and the cost is negligible. Every time you adjust or replace the breaker points, the ignition timing must be checked and, if necessary, adjusted. No special equipment other than a feeler gauge is required for point replacement or adjustment, but a dwell meter is strongly advised. A magnetic screwdriver is handy to prevent the small points and condenser screws from falling down into the distributor.
Point sets using the push-in type wiring terminal should be used on those distributors equipped with an R.F.I. (Radio Frequency Interference) shield (1970-74). Points using a lockscrew-type terminal may short out when installed in these distributors due to contact between the shield and the screw.
- Disconnect the negative battery cable. Loosen the distributor cap by either unscrewing the captive retaining screws or by pushing downward and turning on the spring loaded latch screws, as applicable. Remove the distributor cap from the assembly and position aside. You might have to unclip or detach some or all of the plug wires to remove the cap. If so, tag the wires and the cap before disconnecting the wires in order to ease installation.
- Clean the distributor cap inside and out using a clean rag. Check for cracks and carbon paths. A carbon path shows up as a dark line, usually from one of the cap sockets or inside terminals to a ground. Check the condition of the contact button inside the center of the cap and the inside terminals. If wear, cracks or carbon paths are present, cap replacement is required.
- Either, pull the 6-cylinder rotor up and off the shaft or remove the two screws and lift the round V8 rotor from the distributor assembly. There is less danger of losing the screws if you just back them out all the way and lift them off using the rotor. Clean off the metal outer tip if it is burned or corroded, but DO NOT file it. Replace the rotor if it is necessary or if one was supplied with your tune-up kit.
- Remove the radio frequency interference shield if your distributor has one. Watch out for those little screws! The factory says that the points don't need to be replaced if they are only slightly rough or pitted. However, sad experience shows that it is more economical and reliable in the long run to replace the point set while the distributor is open, than to be forced to do this at a later (and possibly more inconvenient) time.
- Pull one of the two wire terminals from the point assembly. One wire comes from the condenser and the other comes from within the distributor. The terminals are usually held in place by spring tension only. There might be a clamp screw securing the terminals on some older versions. There is also available a one-piece point/condenser assembly for V8s. The radio frequency interference shield isn't needed with this set. Loosen the point set hold-down screw(s). Be very careful not to drop any of these little screws inside the distributor. If this happens, the distributor will probably have to be removed to get at the screw. If the hold-down screw is lost elsewhere, it must be replaced with one that is no longer than the original to avoid interference with the distributor workings. Remove the point set, even if it is to be reused.
- If the points are to be reused, clean them with a few strokes of a special point file. This is done with the points removed to prevent tiny metal filings from getting into and damaging the distributor. Don't use sandpaper or emery cloth as they are not fine enough and will usually cause rapid point burning.
- Loosen the condenser hold-down screw and slide the condenser free of the clamp. This will save you a struggle with the clamp, condenser, and the tiny screw when you install the new one. If you have the type of clamp that is permanently fastened to the condenser, remove the screw and the condenser. Again, be careful not to lose the screw.
- The distributor cam lubricator should either be switched or replaced at each tune-up. If your distributor is equipped with the round kind, turn it around on its shaft at the first tune-up and replace it at the second. If you have the long kind, switch ends at the first tune-up and replace it at the second.
Don't oil or grease the lubricator. The component's foam is impregnated with a special lubricant.
If your tune-up kit did not supply a lubricator, your distributor is not equipped with one, or it looks like someone removed the lubricator, don't worry. Under these circumstances, just rub a match head size dab of grease on the cam lobes.
- Install the new condenser. If you left the clamp in place, just slide the new condenser into the clamp.
- Replace the point set and tighten the screw on all V8 engines that are equipped with a hex adjuster bolt. Leave the screw slightly loose on 6-cylinder engines or any distributor that does not contain an adjustment bolt. Connect the two wire terminals, making sure that the wires don't interfere with any moving components within the distributor assembly. Some V8 distributors have a ground wire that must go under one of the screws.
- Check that the contacts meet squarely. If they don't, bend the tab supporting the fixed contact.
If you are installing preset points on a V8, go ahead to Step 16. If they are preset, it will say so on the package. It would be a good idea to make a quick check on point gap, anyway. Sometimes those preset points aren't.
- Turn the engine until a high point on the cam which opens the points just contacts the rubbing block on the point arm. You can turn the engine by hand if you can get a wrench on the crankshaft pulley nut, or you can grasp the fan belt and turn the engine by hand if the spark plugs are removed to relieve compression.
An alternative is to bump the starter switch or use a remote starter switch. Though using the starter is not a very accurate method and will usually require multiple attempts.
- On a 6-cylinder engine, there should be a screwdriver slot near the contacts. Insert a screwdriver and lever the points open or closed until they appear to be at or near the gap specified in the Tune-Up Specifications. On a V8, simply insert a 1 / 8 in. hex wrench into the adjustment screw and turn. The wrench is sometimes supplied with a tune-up kit.
- Insert the correct size feeler gauge and adjust the gap until you can push the gauge in and out between the contacts with a slight drag, but without disturbing the point arm. This operation takes a bit of experience to obtain the correct feel. Check by trying the gauges 0.001-0.002 in. larger and smaller than the setting size. The larger one should disturb the point arm, while the smaller one should not drag at all. Tighten the 6-cylinder point set hold-down screw, then recheck the gap, because it often changes when the screw is tightened.
- After all the point adjustments are complete, pull a white index card through (between) the contacts to remove any traces of oil. Oil left on the points will cause rapid contact burning.
You can adjust 6-cylinder dwell at this point, if you wish.
- Replace the radio frequency interference shield, if equipped. You don't need it if you are installing the one-piece point/condenser set. Push the rotor firmly down into place, taking care to make sure it is firmly seated. The rotor will only install one way, but if it is not installed properly it will probably break when the starter is operated. Tighten the V8 rotor screws.
- Install the distributor cap and connect the negative battery cable.
- If a dwell meter is available, check the dwell.
These engines use the breakerless High Energy Ignition (HEI) system. Since there is no mechanical contact, there is no wear or need for periodic service. There is an item in the distributor that resembles a condenser; it is a radio interference suppression capacitor which requires no service.