Bryan,
The powdery residue is oxidation. You probably can clean it off. Are those contacts aluminum? If so, you can probably clean them satisfactorily, but eventually the cap will have to be replaced.
What you are seeing on the rotor tip is probably just the effect of the spark jumping the gap- the current flow is from the rotor tip to the cap, in case you are curious. Those contacts are not known for metal transfer, but if there is, I would suspect build-up on the cap terminals, rather than on the rotor, because the rotor tip is negative with respect to ground during the spark, although only about 1000-1500 volts negative during the spark. But that idea of metal transfer is only a guess.
If there is a condensor on the coil, it is for radio noise supression if the truck has/had a radio. It should be connected to the positive terminal. The radio condensor is not the same capacity as the ignition condensor.
The octane selector permits easy adjustment to timing, advance or retard, according to the scale on the bracket and a mark on the distributor pad. The original purpose was to permit quick timing adjustment to accomodate variation in fuel octane rating, which varied quite a bit in past years (distant past years). You shouldn't need to use that adjustment after setting the timing properly, but you can change it if you like, to see what happens. Probably, you won't notice much change, except detonation/spark knock if you go too far advanced.
From your earlier post, use the dwell setting as your reference, rather than trying to get the points precisely set with a feeler gauge. And don't worry about being off a couple of degrees of dwell. Lower dwell is better than higher dwell anyway, unless you are planning to race the truck. But set the timing after all the point adjustments.
With your distributor, you should not see any dwell change beyond a degree or two when you increase engine speed from idle. Lower is better, no change is ideal.
Harvester
