318 Engine stumble

Agreed on the transition. That is why to look at the float, secondary slots, etc. They all sound good. But crud in the wells, air or main jets, or even cracks in the metering body can upset all of that.

Now go back to post #2. That suggests looking at the vacuum secondary control. If the spring in the vacuum pod is weak or someone put in a really light spring, it can open prematurely.

A weak spark will also cause odd flat spots; certain fuel-air mixtures and operating conditions require more spark energy and a weak system can make it fire OK under some conditions but break up under other. So you gotta keep plugging through all of the ignition parts.

You are right to suspect the condensor; it takes specific equipment to test. Easier to just replace.

It don't recall your coil or anything. If you have a voltmeter with ohmmeter, do the following:
- In ohmmeter mode on the lowest scale, touch the leads together directly a few times and take note of the average resistance of the leads.
- Disconnect one side of the coil and measure resistance between the coil + and coil -; subtract the lead resistance and it ought to be around 1.5 ohms for a sotck type coil
- Disconnect one side of the ballast resistor and measure across the terminals; subtract out the lead resistance and for a stock ballast, it ought to be around 0.6 ohms.

Worn distributor cam means you can't the gap and dwell relationship right; if you open the gap on a worn cam, then the dwell gets too short and you can't get the coil charged. Too much dwell or too small of a points gap mans the points don't open far enough to get a proper spark discharge. (Same for too small of a gap...)

You seem to have an odd situation there; right gap.... but long dwell. The more I think about it, I can't wrap my head around why unless it is worn shaft bushings and that is throwing off the gap measurement.