I have had problems with the Holley pumps , I use the Carter usually but I drill the openiings behind the fittings out to 5/16 or a bit larger , at least to match the hole inside the fittings , they seem to flow enough for the engines I have built , be careful though Carter misboxes the Big block Dodge pump with another pump often , if the pump touches the block or doesn`t have 8 bolts holding it together you have the wrong pump , return it