I am trying to find out if there is really a need for the fuel return line I have in my car. The reason I ask is because all the aftermarket mechanical fuel pumps ( Holley and edlebrock with a high flow rate GPH) come with the fuel in and out to the carb, not a return connection. I will need to go to a higher output pump with my rebuild and cant find a Mech pump that has the return line hook up so is there a need to have it and if not, I know I need to replace the in tank sending unit to a one line unit and if I remember correctly I will need a vented fuel tank cap? Thanks all in advance!
They also have one rated for 1100 HP if so desired.
2012 Mustang Boss 302 #1918, Competition Orange. FGF replacement 2006 Mustang V6 Pony, Vista Blue. Factory ordered. 2019 BMW X3 (Titled to the wife, but I'm always driving it for her. So I'm claiming it) Old projects, gone but not forgotten: 1967 FB 400, original CA car. After 22 years of work, trashed by the guy who was supposed to paint it. I had to sell it. 1980 Turbo Trans Am 1970 Mustang fastback, 351C 4Bbl, auto 1988 Mustang GT, 5 speed 1983 F-150 4x4, built 302 1994 Chevy K2500 HD 4x4, 454 TBI
Yes, the OEM 1/4 inch return line is for vapor return. EFI systems are the ones that really circulate fuel between the engine and tank.
2012 Mustang Boss 302 #1918, Competition Orange. FGF replacement 2006 Mustang V6 Pony, Vista Blue. Factory ordered. 2019 BMW X3 (Titled to the wife, but I'm always driving it for her. So I'm claiming it) Old projects, gone but not forgotten: 1967 FB 400, original CA car. After 22 years of work, trashed by the guy who was supposed to paint it. I had to sell it. 1980 Turbo Trans Am 1970 Mustang fastback, 351C 4Bbl, auto 1988 Mustang GT, 5 speed 1983 F-150 4x4, built 302 1994 Chevy K2500 HD 4x4, 454 TBI
The return fuel line will reduce the possibility of vapor lock as the fuel can circulate back to the tank that is being held back by the pressure regulator. Plus, pressure regulators tend to work best when they can bleed off excess fuel via a return line.
RobbMC indicates : Allows “vapor return” line to be used with RobbMc pump. Reduces the chance of vapor lock and improves hot starts.
On hot days, fuel vaporization can greatly reduce pump efficiency and cause erratic fuel pressure. Vaporization can best be reduced by keeping engine coolant temperature under 180 degrees F. Vaporization can also be reduced by using a vapor return line, running race/aviation gas, using a “cool can” to cool the fuel, rerouting the fuel away from the exhaust, wrapping the fuel lines with insulating material, and by reducing the restriction in the lines by using larger lines or fewer bends. ~If a vapor return line is connected to the regulator, the RobbMc VR fitting must be used. Using a different fitting will cause a severe loss of pressure unless the fitting has a .030" to .040" diameter restriction.
