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Home Forums Customer Support Fuel pump sizing/return sizing

This topic contains 2 replies, has 1 voice, and was last updated by  Neil C 1 year, 9 months ago.

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  • June 8, 2016 at 10:57 am #7043

    Neil C

    Hi all,

    I’m looking to purchase a bypass regulator and fuel pump from you to try and get over some vapour lock issues I’m having with my old 1956 Austin Healey 100 Le Mans. It runs twin 1 3/4″ SU carbs and generally these carbs like about 1.5 psi. The issue is that the float bowls are very exposed to the manifolds even with a shield and eventually in heavy traffic and thanks to the ethanol in modern fuels, I’m getting pretty bad fuel evaporation.

    Having done all I can to reroute fuel lines and shielding the carbs, I was thinking of running a bypass regulator and a return back to the fuel tank.

    Q1 – I was looking at a 52503-1-L-L. I’m assuming the fuel will get cycled through the float bowls in this setup and it won’t act like a dead head pump even with the bypass?

    Q2 – The lowest pressure pump Fuelab sells seems to be about 15 psi and 160 gph, I only need about 15 gph 😉 as the car only puts out about 120 bhp.. Will I have any problems with the return line pressure if most of the pump pressure is going back via the return line and not being consumed by the carbs? Can I avoid any issues by fitting a greater diameter return line?

    Thanks for the help.

    June 8, 2016 at 2:13 pm #7047


    Do the carbs have an inlet and an outlet or just an inlet? Meaning – does the system deadhead at the carbs? If so, a bypass regulator won’t really do you any good, at least not when it comes to fuel heat soaking in the carbs. The fuel will still sit in the carb until it’s used. If there’s an “in” and an “out”, I would look at part number 51506-1-L-L. That regulator has the same pressure range as the part number you listed, but it has dual inlets (one from each carb) and a return on the bottom of the regulator. The regulator you listed is only a single inlet.

    Our pumps can go much lower than 15psi and they do have a built in speed control. However, even on low speed, our smallest pump would be pretty extreme overkill. As much as it is my job to sell our products, I think you would be better served (in terms of performance and money spent) by going with a smaller pump. Maybe try looking at an OEM pump from another vehicle. Just about any fuel pump from a modern vehicle would be up to the task, especially since you’re planning to convert to a return style fuel system. An OEM pump is going to take up much less room as well, which I assume would be pretty important on something like an Austin Healey. Our pumps are roughly the size of a beer can and most OEM pump would be about half that.


    Let me know if you have any other questions!

    June 9, 2016 at 4:23 pm #7050

    Neil C

    Many thanks for the advice Josh.

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