Changed the points, Set dwell and timing. Reset float levels( holley 670 Street Avenger), Adjusted mixture w/ vacuum guage. Surge/Jerkiness now gone.
How old are your ignition system components and what is the condition of the disributor?
I look forward to other's comments on this subject as well. Others are more qualified for diagnostics than I.
Footnote: I switched to full manifold vacuum( for vacuum advance) as per John Z's advice.
I am using the 266 distributor from my 302 and it is in perfect condition and has the limiting sleeve for the shortened advance - threw in a Pertronix Ignitor II a couple of years or so back replacing the points so dwell and adjustments are not applicable here. Aside from points I wondered if the weights might be sticking since the car sits 10 moths of the year - but assumed it wouldnt idle down well if they were doing that.
What's with the full manifold vacuum? - I had heard a bit about it in the past but I must admit I am not quite sure where to obtain it from - right now I am pulling from a port on the front passengers side of the carb approximately 1/2 - 2/3's of the way up the metering block and I suspect that is what is considered ported vacuum. How do I get full - right off the manifiold somehow? And what does it do better than the ported type?
I just went out and looked at the carb and I see that the port that is on the front of the base plate that I had capped (which might be a full vacuum port?) has a very small tear in the end of it it so I will try another one to replace it - could it be that is maybe all it could take - hard to imagine but I will try it anyway...
I haven't yet as I said, tried anything to cure this surging problem and was just hopefull the majority of any and all suggestions posted back would help me cut down on the things I would need to try before I could get it solved.
The full vacuum is interesting but I seem to recall putting the dist canister line on the lower post that I mentioned and I couldn't get the timing to settle down at idle sufficiently to warrant using it. - Thanks for you input - Randy