I HAD TWO OF THOSE GLASS FILTERS ON A 800CFM EDELBROCK CARB, THAT I DRILLED AND TAPPED TO MAKE A DUAL FEED OUT OF. THEN WENT TO A 800 CFM HOLLEY. I HAD A FILTER ON EACH 3/8 LINE GONG INTO THE DUAL FEEDS , THE 406 SBC WOULOD RUN OUT OF GAS , EVEN W/ 2 OF THEM, THEY ARE JUNK IN MY BOOK/ FOR PERFORMANCE !