How to Set the Dwell Angle in the Ignition of a 302 Fordby Robert Bayly
Early 302 engines use a distributor with a point and condenser setup. In this type of distributor the coil is triggered by the opening of the points, which ride on an eight-sided cam mounted on the distributor shaft. This causes the coil to discharge and send the spark, also known as secondary voltage, through the center of the distributor cap to the rotor. The rotor sends the spark to the individual spark plugs as it rotates on the distributor shaft. There are two specifications used to set the points: gap and dwell. Dwell is directly related to the point gap and is measured in the number of degrees of distributor rotation that the points are open. This measurement is checked with a tach/dwell meter. Using dwell angle is the preferred method of setting points.
Attach the tach/dwell meter to the 302 by clipping the red wire onto the positive "+" side of the coil and the black wire to the negative battery terminal. Set the meter to dwell.
Start the engine and read the dwell angle. It should be 29 degrees for manual transmission and 27 degrees for an automatic. If not, remove the distributor cap by unscrewing the two screws that hold down the distributor cap. Remove the cap.
Bump the engine with the starter until the points open.
Loosen the two screws that hold down the points about a half a turn with the flat head screwdriver. You want them to still have pressure on the points. If the dwell number was too high, you need to slightly close the points. If the number was low, you need to slightly open them. Look at the metal base of the point assembly. You will see a notch in the metal part that screws down onto the distributor. You will also see a small pin sticking up from the base of the distributor, right next to the notch. adjust the points by placing the tip of the screwdriver in the notch and against the pin, then turn the screwdriver to open or close the points. Note that the amount you want to move the points is very small.
Tighten the two screws that hold the points. Replace the distributor cap. Start the engine and check the dwell angle again. If the reading is off, readjust the points. When finished disconnect the tach/dwell meter.
- Because of timing chain wear, your dwell angle will not be dead on. A plus or minus 2 degree reading is fine. Setting the dwell angle automatically sets the point gap.
Things You'll Need
- Tach/dwell meter
- Flat head screwdriver
Robert Bayly, based in Apple Valley, California, began writing in 2010, his "how to" articles can be found on eHow. With more than 15 years in the auto industry, Bayly has been an auto and diesel mechanic, service writer and parts manager. He received certificates from Pontiac (parts system), Cat Diesel (engine service), Saab and Fiat (parts- warranty system).