The following information has been borrowed from: http://www.volvoamazonpictures.se

Ignition Settings

The ignition order is 1-3-4-2 clockwise on the B16 engine and counter-clockwise on the B18 and B20 engines. There are different recomendations for the sport engines (B and D editions), but Volvo has been consistent on the A editions. The settings below are valid for an engine that has reached its working temperature, has the vacuum regulator disconnected (if present) and at 1,500 rpm, unless otherwise is indicated. Keep in mind that a lot has happened since these settings were defined by Volvo. The octane ratings (or rather the definition for them) have changed, the engine is worn, ignition parts have been changed over the years and a lot of other things that can affect the ignition settings. Don't be surprised if the ignition needs to be set according to other values than those listed here in order not to ignite too early (spike) or too late (excessive fuel consumption). Turn the distributor counter-clockwise for an earlier ignition and clockwise for a later ignition on the B16; the other way around for B18 and B20.

* With emission control.
** At maximum 850 rpm.
*** At 600 - 800 rpm.