I measured the dual ballast resistor today, Primary side is slight out of bounds, measured 1.9 Ohm (should be 1.12 to 1.38 ohm) and the auxiliary side measured 5.2 Ohm, which should be OK.
Not sure how the primary side 1.9 Ohm would show up when running at idle.
In theory, yes. That's because the less current through the coil means less energy available to the spark plug.
In reality I don't know. If there is enough voltage to initiate and enough current to build the flame kernal enough to get a a good burn, then more spark energy won't help. But if its having trouble developing a good burn, then having more energy should help.
This could be seen on an oscilliscope, but I understand you don't have one. Most people don't.
While you have the ohmmeter out, check the coil primary resistance.
The other thing to experiment with is whether changing the fueling smooths out the rpm differences.
We don't know the 'best' for that engine, rpm and timing, but we know its close. Close enough to make small changes and observe the effect.
If slightly richer than current setting results in slightly smoother engine, then check it in gear for rpm and vacuum drop. I'd like to see less than 75 rpm drop going into gear.
If slightly richer causes reduction in rpm, then its definately too rich.
If slightly leaner causes an in increase in rpm, then try shifting into gear (same comments as above).
If slightly leaner causes more variation in rpm, and over all drop in rpm, then its a little too lean.
Depending on the results, I might be very tempted after doing the above to set timing at 10 or 11*, same rpm, and repeat these tests.
I know its a lot of fuel to use testing. But it you want to fine tune a not quite stock engine setup, its what has to be done. Next time you'll have more experience and knowledge, but first time we have to hear, see and smell it for ourselves.
This is following up on this post by
@nm9stheham
Compression test on a 360, result OK or not?
