See Figure 1
Dwell angle is the amount of time (measured in degrees of distributor cam rotation) that the contact points remain closed. Initial point gap (0.019 in.) determines dwell angle. If the points are too wide they open gradually and dwell angle (the time they remain closed) is small. This wide gap causes excessive arcing at the points and, because of this, point burning. This small dwell doesnt give the coil sufficient time to build up maximum energy and so coil output decreases. If the points are set too close, the dwell is increased but the points may bounce at higher speeds and the idle becomes rough and starting is made harder. The wider the point opening, the smaller the dwell and the smaller the gap, the larger the dwell. Adjusting the dwell by making the initial point gap setting with a feeler gauge is sufficient to get the car started but a finer adjustment should be made. A dwell meter is needed to check the adjustment.
The ignition timing must be checked and adjusted any time the point set is replaced or the dwell is changed. When the dwell is increased, the ignition timing decreases, and vice-versa.
- Run the engine to normal operating temperatures and then let it idle.
- Raise the adjusting window on the distributor cap and insert a 1 / 8 in. allen wrench into the adjusting screw.
- Turn the adjusting screw until the specified dwell angle is obtained on the dwell meter.