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How to Set the Points in an Old Truck

Breaker point distributors were standard equipment on most vehicles prior to the 1970s. The point distributor has a cam-type lobe that opens and closes the breaker points. When the points close, primary voltage is sent to a coil, and the coil sends high voltage to ignite the fuel charge via the spark plug. This sequence is timed for each cylinder as the engine rotates. The distributor cap must be removed to adjust the point gap on most distributors. GM trucks have a small door molded into the cap that provides access to adjust the points while the engine is running.

Instructions

Adjust the Points With a Feeler Gauge

1

Pull the keys from the ignition and pop the hood of the truck. Locate the distributor cap and follow the center ignition wire from the distributor cap to the coil and remove this wire. Most coils mount on top of the engine or the top side of the firewall.

2




Unsnap the clips or remove the screws that hold the distributor cap in place and lift it off the distributor.

3

Remove the rotor button from the top of the distributor shaft. Some rotors are attached with screws, and others just seat over the shaft into a groove to keep the rotor properly aligned.

4

Turn the distributor shaft by rotating the fan blade by hand until the high spot of the distributor lobe opens the contact points or is under the fiber bridge. Turning the fan may require that slight pressure be applied to the fan belt in the direction that the fan is turned.

5

Loosen, but do not remove, the screw that allows the breaker points to move in or away from the distributor shaft.

6

Place a .019-inch feeler gauge flat between the contact points and move the points in or out until the feeler gauge just fits between the contacts. Once adjusted, tighten the hold-down screw. Recheck the point gap, after the screw is tightened, to ensure that the feeler gauge retains the proper fit. If the gap is not right, repeat the adjustment.

7

Insert the keys into the ignition and turn the engine over while an assistant checks to see that the breaker points open and close properly as the distributor shaft rotates.

8

Install the rotor button on the distributor shaft. Look under the rotor button. Some rotors have a square and a round peg that must be inserted in their respective locations. Other rotors just slide into a groove.

9

Replace the distributor cap and coil wire.

Adjust Points With a Dwell Meter

10

Connect the positive lead of a dwell meter to the primary coil wire that comes out of the distributor. Ground the negative lead.

11

Crank the engine over when dwelling the points and observe the gauge reading.

12

Adjust the points contact gap, when dwelling the points, to change the dwell reading. Refer to a service manual for your trucks make, model and year to get the correct number for dwelling the points. Use the same method to adjust the points as in Section 1 but without the feeler gauge.

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