A return-style regulator, or dynamic system, positions the inlet and outlet ports above the check valve with only the return volume serving to flow through the restriction. As a result, the pressure from the pump to the fuel regulator is the same as from the fuel regulator to the carburetor (typically 8-9 psi), which allows the pump to speed up, increasing volume significantly, and supplies constant full output to the float bowls.
The benefits of a dynamic, return-style fuel system are longer pump life, the elimination of unwanted pressure drops, a marked increase in pump-to-horsepower ratings, and quieter pump operation. This all means that a dynamic system allows for a more consistent air/fuel ratio across the rpm band and more predictable power all the way down. The only drawback to a dynamic system is the increased cost of fittings and lines.
Fit To FlowBefore installing any fittings, take a look inside. Not all fittings are created equal, and the wrong fitting can cause a restriction in your system. Most fittings supplied by the high-performance aftermarket are designed to maintain good flow, whereas those purchased from hardware stores or auto parts chains are more often sub par, often due to small id sizes.
When routing hard line or stainless braided AN lines, always avoid sharp-radius turns. Take time to map out your lines, and route them in a manner that provides the smoothest bends away from heat, suspension items, jacking points, and areas where the line could be impacted on the road or track. Depending on your application, you may opt to run a heat sink to reduce the fuel temperature.
When selecting stainless braided AN lines, choose a size that will flow well enough to support your requirements. All AN sizes use a dash (-) preceding the number referring to the 1/16-inch-od thin-wall hard line to which the flexible line will compare. As an example, an AN-8 line would have the minimum id of an 8/16-inch (8/16 = 1/2). For most performance applications you'll want to run AN-8 or larger.