WEEKEND WORKSHOP

Set timing approximately 9

Locking the mechanical advance will have altered the timing. Make sure the crank timing marks are still aligned. Turn the ignition on and rotate the distributor until the Amethyst’s red light goes off. The marks you made in step four should be aligned.

Calculate map 12

Calculate the midpoints of the centrifugal and vacuum advance ranges in your manual (eg, in the example given in the last step, the midpoint would be 9°@1600rpm). Install the software and connect your computer to the control unit.

Set timing exactly 10

The previous step will have set the timing well enough for the engine to start. Set it exactly using a strobe with the engine at tickover, then lock the distributor pinch bolt. The engine’s now using a default ignition map. It needs to be fine-tuned.

Set ignition map 13

‘Map 1’ is the unit’s default map. It’s a good idea to retain this as a reference. Start the engine and enter the map figures calculated from the workshop manual. Save this as ‘Map 2’. Adjust the idle speed at the carburettor(s) if necessary.

Find advance data 11

Check your workshop manual for distributor advance curves. They’re usually given as ranges of advance in degrees at various engine speeds (eg, 7°-11°@1600rpm). Make sure the figures are for crankshaft advance, not distributor advance.

Fine-tune the map 14

Let the car warm up, then go for a test-drive. Listen for pinking, especially when you floor the throttle at low-to-medium revs. Try incrementally adding more advance across the map. Retard it a step-or-two when pinking becomes evident.