Thread: sbc 350+edelbrock 1406 - fuel return line?

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Your Edelbrock 1406, and any other modern 4-bbl carburetor, will operate best with fuel pressure of 4 3/4 to 5 psi at the bowl inlet. Pressures over that can overpower the needle and seat in the bowl and allow the pump to blow raw fuel into the intake manifold, creating a tuning nightmare for you. This is not fuel injection, where more pressure can make more hp, it is carburetion, a whole different animal.

What I like to do, on all new or different installations, is to tee off at the carb and run a mechanical line back to the firewall, then up past the hood lip, onto the cowl in front of the windshield. I like to temporarily mount a mechanical, 0-15 psi, liquid-filled gauge so I can read it through the windshield as I drive down the road. It only needs to be there temporarily until you get the pressure dialed in, so usually using duct tape and tie wraps will suffice.

To run a return line off a mechanical pump, you will need a pump with 3 openings. One is suction from the tank, one is pressure to the carb and the third is a return line to the tank. I highly recommend using only generic pumps from Carter or Airtex.

In my experience, a pressure regulator will not work well with a mechanical fuel pump due to the pulses generated by the pump. Regulators work well with an electric pump, because the pressure generated is rather steady. So, it's best to choose a mechanical pump that has limited pressure in the first place and use it without a regulator. By the time this return port pump pushes the fuel uphill to the carb, it will likely be in the 5 psi range.....
http://www.summitracing.com/parts/cr...make/chevrolet

If you don't want to fiddle with a return line, use a standard 2-port pump....
http://www.summitracing.com/parts/cr...make/chevrolet

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