- Disconnect the high tension wire from the top of the distributor and the coil.
- The distributor cap is retained by two spring clips. Insert a screwdriver under their ends and release them. Lift off the cap with the spark plug wires attached. Inspect the inside of the cap. Wipe it clean with a rag and check for burned contacts, cracks and carbon tracks. A carbon track shows as a dark line running from one terminal to another. It cannot be successfully removed, so replace the cap if it has one of these. Generally, a cap and rotor will last 36,000 miles (58,000 km).
- Remove the rotor from the distributor shaft by pulling it straight up. Examine the condition of the rotor. If it is cracked or the metal tip is excessively worn or burned, it should be replaced. Clean the metal tip with a clean cloth, but don't file it.
- Pry open the contacts of the points with a screwdriver and check the condition of the contacts. If they are excessively worn, burned or pitted, they should be replaced.
- If the points are in good condition, adjust them and reinstall the rotor and the distributor cap. If the points need to be replaced, follow the replacement procedure given next.
REMOVAL & INSTALLATION
- Remove the cap and rotor. Clean the cap and rotor with alcohol, or wipe them clean with a rag.
- Remove the two Phillips screws that secure the points to the breaker plate.
- Remove the condenser terminal lead and the ground lead from the points.
- Remove the screw which secures the condenser to the outside of the distributor body. Remove the condenser lead from the terminal.
- Install a new condenser and connect the ground lead from the points and the the condenser terminal lead.
- Install new points, but do not fully tighten the securing screws.
- To adjust the point gap, rotate the crankshaft until the contact heel of the points rests on a high point of the distributor cam.
- Place a flat head screwdriver between the outer wall of the distributor and the bottom plate of the points so that the contacts can be opened by turning the screwdriver.
- Place a feeler gauge of the proper thickness between the breaker points and adjust the points so that a slight drag is felt when the feeler gauge is removed. Tighten the Phillips head screws, being careful not to lose the proper point gap.
- Recheck the gap after tightening.
- Lubricate the cam surface, rubbing block, arm pivot, and distributor shaft with distributor grease, which is available from auto supply stores.
- Reinstall the rotor and distributor cap, making sure that the spark plug wires are installed tightly on the top of the cap.
The dwell angle is the number of degrees of distributor cam rotation through which the points remain closed (conducting electricity). Increasing the point gap decreases dwell, while decreasing the gap increases dwell.
The dwell angle may be checked with the distributor cap and rotor installed and the engine running, or with the cap and rotor removed and the engine cranking at starter speed. The meter gives a constant reading with the engine running. With the engine cranking, the meter will fluctuate between zero degrees dwell and the maximum figure for that setting. Never attempt to adjust the points when the ignition is on, or you may receive a shock.
- Connect a meter as per the manufacturer's instructions (usually one lead to the distributor's terminal of the coil and the other lead to a ground). Zero the meter, if necessary.
- Check the dwell by either the cranking method, or with the engine running. If the setting is incorrect, the points must be adjusted.
- To change the dwell angle, turn the ignition off, loosen the points hold-down screw and adjust the point gap; increase the gap to decrease dwell, and vice-versa. Tighten the hold-down screw and check the dwell angle with the engine cranking. If it seems to be correct, replace the cap and rotor and check dwell with the engine running. Readjust as necessary.
- Run the engine speed up to about 2000 rpm, and then let the speed drop abruptly. The dwell reading should not change. If it does, a worn distributor shaft, bushing or cam, or a worn breaker plate is indicated. The parts must be inspected and replaced, if necessary.
- Ignition timing must be checked after adjusting the point gap, as a 1° increase in dwell results in an ignition timing retard of 2°.