Dual point distributor ID question

I don't know what all can cause that. Certainly carb/ vacuum advance mismatch, engine using some oil (valve guides), too lean or too hot, not sure what else. "Back then" for awhile I had a 71 high compression 340 in an old Landcruiser, and typically ran either Holley spread bore or QJ 4 bbl. Seems to me the QJ always had that problem, heavy "lug" load, part throttle rattle. On the other hand I used to run "plenty" of timing, and likely too much LOL