Micrometer Timing Control

A further refinement is that the static position of the contact-breaker baseplate can be varied over a small range of timing by rotating the knurled nut on the vacuum timing control without disturbing the main setting of the distributor. Each of the divisions that registers with the edge of the housing represents a change in timing of 4 degrees at the crankshaft, so that the setting should not be altered more than, say, half a division at a time. As it is difficult to see the scale when the distributor is in place on the car, it is worth remem¬bering that 13 to 14 clicks of the knurled adjusting knob are equivalent to one degree of timing. Also, when viewing the distributor from above, as fitted to the engine, clockwise rotation of the knob advances the ignition and anti-clockwise rotation retards it. Incidentally the opposite directions

Timing marks on the flywheel of a manual-gearbox model







of rotation are quoted in the earlier official Driver's Handbook and Work-shop Manual, presumably being based on the direction as seen when the knob is viewed from the end of the spindle—i.e. with the distributor re-moved from the engine—so watch this point when adjusting the ignition.