850 Ultra XP lean bogs when secondaries open

The best method I've found is to hold your phone over the carb and video it while someone mashes the throttle. You will see/hear what happens. Is the pump shot late? Too short? Too long?? (Another member on here was doing this video method and I picked up on it and found it quite helpful.)

I've found that the pump shot is usually too short and the bigger 50cc pump with a smaller rear nozzle (33-35) makes for a longer shot that carries through the transition. My 408 has an 850 Holley-style with a Super Victor so that's how I solved the riddle. Has 2 50cc pumps and 37 shooters in front and 35 in back (both are tibes shooters).

Of course pump cams and hole position of those cams also matters. I find that hole position 2 is useful if you stage the car with the throttle partly open (like I do holding it at about 2200-2400 rpm). Position 2 usually gives you more of a given cam whereas position 1 is already partly "used up" at that throttle position.

As for jets, I'm at 81 frt & 82 rear. Picked up 1/2 mph when I leaned the front out so gonna lean it out again and see what happens. Plugs still look dark so we shall see....