I never been a fan of the 50 CC pumps on any Holley carb., no matter what size I have changed the rear 50 CC pump to a 30 CC pump and ended up with better 60 ft times on a bracket 440 motor with a Holley 800 D.P. carb. I did the same thing on a SS style Hemi motor with a stock crossram that had dual 750 D.P. carbs with 50 CC pumps on the rear, we changed them to 30 CC pumps(you have to change the pump arm also ) and put in 31 squirters to get the best 60 ft. times that day at that track I would adjust the accelerator pump arms like Holley says to and go from there You can slow the 60 ft. times down with to much accerator pump shot is what I'm trying to say