are your sec throttle plates opened the right amount?

What happened when your timming was advanced to 18-20 initial? Did it have more time to burn and smooth out. A stroker engine thats close to square has unusual timming demands. Some take alot of advance with little curve to get running proper.

I think your going in the right direction. You could raise the float level too but MAB is the most logical step. Also, if you richen the IFR it will run richer from off idle until the main circuit comes in - might help. But if it is fine at 1800 rpm could be the wrong fix. I would consider that last.

I do agree I would try some wire in the MAB's to see if they are pulling enough fuel yet or if that rpm where it happens is to low and its still on the idle/transfer circuit. Once you are sure where (what circuit) it happens you can work it from there. You want no surge but you also dont want to foul plugs and use to much fuel. Now in the old days (60's and 70's) we would just fatten it some with more jet (had no adj MAB's) back then and if it fixed it well then cool. We drive it a few days and make sure it's not fouling the plugs. But now we have much more technology and should be able to tune for about 13 to 1 or so and eliminate the surge. I didnt pay attention to how new the carb is as I have seen worn throttle shaft's cause problems of this nature as it can get pulled and tilt then move enough in the throttle plate and let it pull air in when it should not. I also dont remember if you said you run vacum advance as it can cause a timing issue if not in sync with the mech advance. Anyway just throwing some more idea's your way but you sound like you know what to look for. Good luck and keep us posted on you progress. Ron

Timing was bumped up to 21 initial 36 total no vac advance. Doesn't kick back but does crank better with the spark off then I flip it on to fire. I'm using a silver and a blue spring in the MSD dizzy IIRC. Should be coming in pretty quickly.

The secondary plates are open a little to be able to idle well without uncovering too much transfer slot on the primaries.

Thanks for the last round of answers/ encouragement I appreciate it. No time to fiddle for a few days I'll report back then.

Kevin