Originally Posted by sds10racer
pumps are set up as per holleys' recomendations so as not to bottom out at full throttle. am footbraking. have a 3500 stall.
Not saying the other advice is wrong, just don't do more than one change at a time so you know what works.
First off, since your ft. braking set the front pump so when your staged and at stall speed, you haven't used the entire shot before you need it. The stumble could be caused by not having enough initial shot left. When your at launch RPM you should still have almost all of your front pump shot left. May have to mess with the nozzle size and pump cams to get it right. This should also help your launch. Definately keep the 50cc on the front, 30 on the back should be fine.
How much total timing are you running now and what RPM does your full advance come in?