A single method to check the dwell is to remove the distributor cap and attach to the rotor a cheap plastic circular protractor (use blue tack or double sided sticky tape). Connect a lamp between the body and the distributor low tension terminal. Switch on the ignition and slowly crank over the engine. When the lamp goes off make a note of the protractor reading to some fixed pointer. Crank over the engine until the lamp comes on again and take another reading. The difference in readings is the dwell angle. For a four cyclinder engine this should be 45°. To increase the dwell, reduce the points gap and vice versa. Reset the timing after the dwell setting is done.