A little background:
I am running a Mallory 5250 (250GPH) fuel pump with a 5 port Mallory Fuel Regulator located at the engine firewall with a return line from the bypass port on the regulator to a return fitting located on the bottom of the fuel tank. This gives me a nice circular flow of cool fuel for the engine with two 1/2" lines feeding the carb off the regulator. The engine is a 502 with a 850 Holley and seems to run very well with plenty of fuel.

The Problem:
The fuel pump is realllllly loud. It sounds like it is sucking air. It goes from a scream to smooth and then back to screaming. I checked all fittings including air testing them and no problem. I then sent the pump back to Mallory. The result was that after testing the pump was fine. They did put in a new fitting with a new O ring. I got the pump back and same thing, very loud! I then took the pump and ran one line from the in side and one line from the out side into a bucket of fuel. Same exact thing, very loud. I then took the pump to a racing engine builder and they tested it. Yes, again the pump tested good as far as a dry run. Now here's the question - Should I be running the return line into the bypass fitting on the pump (I presently have a plug in it) or should I leave the return line feeding into the tank. I know these pump can be loud but this is uncommon loud. What do ya think?? Any input is appreciated.

Ken

Ken from what i have read in some post here and Team Chevelle is that you do want to run a return line from the pump to the tank so the pump doesn't over work its self and so it doesn't heat the fuel up from over working the pump with no return line hooked up. I hope this helps you im sure some one here will chime in. Good luck.

Insulate your pump from the chassis.

I think I'm wondering if the pressurized fuel line from the regulator right back to the bypass port located at the pump (which I now have a plug in)instead of returning it to the tank will in a sense almost act as way of quieting down the pump since it have a greater supply of fuel to pump instead of relying on the pump only sucking from the tank which it will still do. I other words will this actually supply more fuel to the pump and in a effect keep the pump from malking that starving sound. Has anyone out there done this before? Keep in mind that this pump is supposed to be a quiet running pump for the volume it pumps (per Mallory).

Thanks, Ken

What size inlet and outlet are you running on the pump? How is it mounted? I have a Mallory 140 and it's not exactly quiet. You can't hear it once the car starts. I am very happy with Mallory pump so far.

Your problem is probably that fuel pumps are made to push fuel, not pull it. It needs to be as close to the tank as possible, read the installation instructions below to verify what I am saying...

http://www.malloryperformance.com/pdf/5250_5250A.pdf

That is a definite possibility as well. I ran a 10AN feed line and 8AN exit. I also made sure it was slightly downhill to the pump. Here is how mine is set up.
http://i200.photobucket.com/albums/aa251/Payback1969/IMG_1249.jpg
http://i200.photobucket.com/albums/aa251/Payback1969/IMG_1251.jpg
I have a 1/2npt to 10an 90 to a 10AN 100 micron filter, to 10 AN hose, to 10 AN 180 degree fitting. Then 8AN or 1/2 inch aluminum line feed and return. I also have a 8 micron filter right before the regulator.

Hey Todd,
Looks nice under there, i have the same fuel filter as you do up next to my mechanical pump. But i never had to clean it yet, my question how easy is it to unscrew the fuel filter and clean without gas poring all over the place.

I haven't done it yet. My orignal plans called for the new filter aeromotive has with the shut off valve. It was just to long. When I do clean it, I'll make sure it's low on gas and disconnect a hose and pump the fuel into a gas can.:beers: