Might need back up and remind us what you’re working with here.
1) Is this an engine that sat for long-ish time that you are trying to revive or an engine you have seen run well that is now running poorly?
2) Have you verified the rotor is pointing at #1 at TDC compression stroke, and that firing order is 1-5-3-6-2-4 from there? Points and condenser new or unknown?
3) Has a valve adjustment been performed?
Not trying to speak condescendingly or anything. When I first tried running my engine, it acted a lot like yours. I wasted some time chasing hunches rather than getting back to the basics. Had the timing 180 degrees out at one point. Bad condenser. Manifold heat riser locked up. A number of things that contributed to poor running, even though I had rebuilt the carb.
Believe it or not, a Stovebolt can run with the firing order all screwed up. I “know a guy” who has seen it happen.
Last edited by JW51; 07/29/2023 1:05 PM.