Dwell angle - checking

Ignition system / Dwell angle - checking

The dwell angle is the number of degrees through which the distributor cam turns between the instants of closure and opening of the contact breaker points.

1 Connect a dwell meter in accordance with the maker’s instruction. The type of meter that operates with the engine running is to be preferred; any variation in contact breaker gap, caused by wear in the distributor shaft or bushes, or the height of the distributor cam peaks, is evened out when using this.

2 The correct dwell angle is given in the Specifications at the beginning of this Chapter. If the angle is too large, increase the contact points gap. If the angle is too small, reduce the points gap. Only very slight adjustments should be made to the gap before re-checking.

3 On Ducellier distributors, adjustment of the dwell angle can only be carried out by switching off the ignition, removing the distributor cap, rotor and spark shield and adjusting the points gap.

4 Re-check once the engine is running.

Adjustment may have to be carried out several times to obtain the correct dwell angle.

5 On Marelli distributors, adjustment of the points gap (dwell angle) is carried out with the engine running by inserting a 3.0 mm Allen key in the hole provided in the distributor body.

6 Always check and adjust the dwell angle before timing the ignition as described in Section 4.