High-PSI, High-Volume EFI fuel pump in carb'ed application...
 

OK, I'm not one to waste money when I don't have to and I'd rather not buy a few (or at least a couple) different fuel pumps and regulators for my 13b swaps. For the next few months, maybe even the next year, the engine I'll be running in my car will be carb'ed. As soon as I can get my project engine finished I'll swap it in, and it will be Haltech injected. I've read a few other places about using high-volume, high-psi EFI fuel pumps in carb'ed applications, but I'm not sure exactly how to go about it...

For the time being, I'm thinking of using the SE pump with the carb'ed 13b. I'd like to run an Aeromotive 1:1 EFI/Carb adjustable pressure regulator (comes with different springs for low or higher pressures). I've seen other regulators that are cheaper and appeal more to me, but I fear this FPR may be my only option...Some other regulators, especially low-psi carb'ed versions, have a small inlet pressure rating for use with a carb style pump. I need a regulator that will regulate down to 3 or 4 psi for the Weber that will be put to use for the next year or so...

If I were to use the stock SE pump, or even a Walbro in-line style that I'm planning on running with my project engine, how can I get the pressure down to 3 or 4psi without the use of the Aeromotive regulator? Would it be possible to route the high-psi fuel through a 1:1 return style adjustable EFI regulator, adjusted as low as possible, then an additional low-psi regulator plumbed into the outlet of the first?

Some more specs and details of my set-up: I have an SE fuel tank and hard fuel line that I may use, I've been thinking of upgrading to at least 3/8" hard lines and possibly -6 AN flexible lines to handle the higher pressures. I'd like to use the same EFI regulator with a turbocharged set-up on my project engine, along with the Walbro pump. I will also upgrade the return line to the tank to 3/8"/-6 AN. I'll use a new in-tank sock filter with the SE tank, and at least two other 3/8" filters in the system-one before the pump and one before the regulator (both low-restriction).

What would be the best way to reduce the pressure in this system to 3-4psi for the Weber DCOE, without having to purchase a different regulator for use with my project engine? I'm planning on either buying the Aeromotive EFI/Carb regulator or two seperate regulators-one a 1:1 return style adjustable EFI and the other a 3-5psi adjustable carb regulator, but I'm not sure if this will work right the way I'm planning. Any suggestions?

Another question kind of off-topic: will 3/8" fuel line from the tank to the regulator and fuel rail support 300BHP?

Thanks for all your help, time, and cooperation guys, I sincerely appreciate it...

use the pump for FI and a regulator to bring the pressure down for the carb. once u finally go FI, u'll probably be able to do away with the regulator all together.

Adjusting fuel pressure
 

Most of the cheap regulators will not handle more than about 15 psi input pressure. There is a cheap and easy solution.

I built a rotary powered GLC about 20 years ago, using a 13b with an RX-4 carb. I wanted more fuel capacity, and I used a 17 gallon tank from a Chevy Astrovan, which had a fuel pump immersed in the tank. The pressure was about 50-60 psi, as I recall.

The carbureted rotary Mazdas have a tee fitting where the fuel line attaches to the carb, and one side feeds the return line to the fuel tank. This return line bleeds fuel back to the tank, maintaining a constant flow of cool fuel to prevent vapor lock. I soldered up the return tube in the fitting, and drilled a very small hole. I then hooked this up to the fuel inlet line and return line, and put a pressure gage on the outlet to the carb. I turned on the pump and measured the pressure, which was too high. I then drilled out the hole a few times, gradually increasing the size of the hole, bleeding more and more fuel back to the tank until the outlet pressure was slightly less than 15 psi.

I then connected the outlet of the tee fitting to the pressure regulator, and from there to the carb. I adjusted the regulator to about 3 1/2 - 4 psi. It ran perfectly for over 140,000 miles, never had any trouble with the regulator. It was one of those cheap, cheesy looking chrome plated regulators.

your running a weber, so you wont have a fuel return line on your carb. You will want to make sure you get a FPR that has the ability to return fuel, otherwise you run the risk of burning out the fuel pump. I believe that holley makes a FPR like that and I know that aeromotive makes one. And get a good fuel pressure gauge.

If your body is an SE to begin with, going to a 3/8" line is actually downsizing. SE lines are even bigger than the FC lines. So far your plan sounds good with the Aeromotive pump.

mallory part #4309 fuel pressure reg.. it can go as low as 3 psi in combo with an efi pump..

Wrongo. It starts at 1/2" from tank. Then drops down to 5/16" under the car. Return is also 5/16".

Cool-thanks to all for your advice. I'll probably stick with the Aeromotive regulator and just swap out the different springs between the carb'ed and EFI applications...

I was under the impression that the SE line was 3/8" coming from the tank, I'm probably wrong because I had never measured it. It just looked to be the same size as the roll of 3/8" hard line I have laying around. Or maybe they're both 3/8" ID...

Stilettoman, that's a cool cheap idea. If I end up running two regulators, cheaper EFI and carb versions, I may have to use your idea with the set-up. I'd place the modified "t" fitting right before the carb regulator...

Again, thanks for all your help and info...