I have always run the 4782 4783 mechanical 6 pack on a 340, 1350 cfm. I had them on a 4 speed cuda and 1st gear 2000 rpm floor it and no stumble just GO GO GO. When all 3 open at the same time it's almost no vacuum so you have to dump a lot of fuel to overcome the air coming in. I have also run 850 cfm holleys on a lot of small blocks, 69 Z28 302 for one.