IGNITION TIMING The contact breaker points gap or dwell angle must be correctly set before attempting to check or adjust the ignition timing. Conversely, the ignition setting should be checked after cleaning, renewing or resetting the contact breaker points.
Static Check During this procedure the engine can be turned over by engaging reverse gear and pushing the car backwards, or by jacking one of the front wheels clear of the ground and rotating the wheel. In this latter case, top gear should be engaged. On automatic models, use a screwdriver inserted through the aperture in the converter housing to rotate the converter by levering on the starter ring gear .
Crankshaft rotation is clockwise, viewed from the radiator end of the engine.
It will facilitate rotation of the crankshaft if the spark plugs are first removed from the engine.
Remove the cover plate from the inspection hole in the clutch housing (rubber plug from the converter end cover on automatic transmission models) to allow observation of the timing scale on the flywheel or torque converter. . A mirror will be required to enable the timing marks to be seen.
Remove the distributor cap and connect a 12 volt test lamp between the distributor LT terminal and a good earthing point.
Rotate the crankshaft in its normal direction of rotation until the rotor arm is pointing approximately midway between the No. 2 and No. 1 segments in the distributor cap. The rotor arm rotation is anti-clockwise viewed from above.
With the ignition switched on, rotate the crankshaft slowly until the test lamp just lights, indicating the points have opened. This gives the firing point for No. 1 cylinder. If the ignition setting is correct, the appropriate mark on the timing scale will now be aligned, with the reference pointer in the inspection hole. Refer to 'Tune-Up Data' at the end of this section for the specified ignition settings.
The setting can be checked by gently pressing the rotor arm in the opposite direction to its normal rotation, when the test lamp should go out until the arm is released again.
It should be noted that late models have a timing scale more sensibly situated on the timing gear cover adjacent to the crankshaft pulley .
If the timing setting is incorrect, it should be adjusted as described below.
Adjustment The 25D4 type distributor is fitted with an ignition timing adjusting device and if only a small correction is required this can be achieved by rotating the knurled adjuster nut on the end of the vacuum unit spindle . One graduation on the vernier scale is equal to about 50 of crankshaft movement and fifty five clicks of the adjuster nut. Turn the adjuster nut in the direction of the cast 'A' mark if the timing mark is past (to the left of) the reference pointer, or towards the 'R' if the mark is before the pointer.
If a large correction is required, the complete distributor body must be turned to obtain the correct setting. This is the method which must be used with the 45D4 type distributor as it does not have an adjuster nut. In the case of the 25D4 unit, first turn the knurled adjuster nut until the vernier scale is in the central position.
Turn the crankshaft until the correct mark on the timing scale is aligned with the pointer in the inspection hole. Slacken the distributor clamp bolt nut and rotate the distributor body anti-clockwise past the point where the test lamp illuminates, then carefully rotate it back clockwise until the lamp just goes out. Tighten the clamp bolt without disturbing the body setting. Finally, recheck the setting as described above.
Dynamic Check If possible the ignition timing should be checked with the engine running using a stroboscopic timing light, as this will ensure optimum engine performance and economy. With later models, it really is essential that the ignition be set dynamically. The timing light should be used in accordance with the equipment manufacturers instructions.
It will facilitate the timing operation if both the reference pointer and the appropriate mark on the timing scale are emphasised with white paint to make them more easily observed.
The distributor vacuum pipe should be disconnected and plugged. With the engine running at the specified speed, the appropriate timing mark should be in line with the reference pointer.
If adjustment is required, proceed as described above. Rotate the distributor body clockwise to advance the setting, or anti-clockwise to retard it.