If you have the stock fuel pick up in the tank you might want to test it to see if it is plugged up with gunk You can hook a flexable fuel hose to the steel line at the pump and blow back into it, if you have to blow really hard to put air into the tank it may be plugged I've seen that more than once, hard gunk gets into the stock pickup in the tank and sometimes in the line between the tank and the front of the car If your car is a early 1960s to mid 1970s and a non Hemi or 440 car it will a have 5/16 O.D.(1/4 inch I.D. ) line stock, even the Max Wedge cars did My 1963 Max Wedge stocker had the 5/16 lines, I added a Holley Blue pump into the line at the rear of the car, I decided to bypass it at a division points race in Las Vegas one year as I had a alternator on the car that was stripped out and not charging, the car ran faster with that pump disconnected I was running a MSD 7 race box and coil I was using the old Carter NASCAR race hemi mechanical fuel pump, the one that has three valves inside instead of two like the other Carter mechanical race pumps had I used that pump per instructions from Mike and Dick Landy That car low elevens with that mechanical pump only after that BTW, I had added another 3/8 pick up in the tank and used a Moroso Y fitting to feed both lines from the tank to the stock steel fuel line going to the front of the car