Supplemental electric fuel pump and regulator rec's

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MopaR&D

MopaR&D

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I have a 750 cfm Street Demon carb on the ~450 HP 360 in my '70 Duster with a stock replacement Carter mechanical pump and stock 5/16" fuel line all the way from the tank pickup to the carb. Fuel supply seems marginal for my power level as after a second or 2 at WOT I can see my AFR slightly leaning out on the gauge for my wideband O2 sensor. Fuel pickup sock is good (replaced it a few years ago) and inside of tank is clean so I know it's not getting clogged. I'm thinking to keep the stock mech pump but add an electric pump that I can switch on when the carb needs extra fuel supply. What recommendations do you guys have? What electric pumps have you used that are reliable and won't be a restriction for the mech pump when not turned on?

Also my Duster is originally from California and has the Cleaner Air System with the funky vapor-capture system (pre-charcoal canister), I'm thinking to modify the extra line from the vapor capture "tube" in the trunk to the engine bay to turn it into a fuel return line so I can use a return-style regulator. I occasionally have minor issues with fuel percolation and I know using a return-type fuel system would help keep the gas going to the carb from getting too hot. So I'd also appreciate recommendations for a good return-style fuel regulator.
 
I would just skip the mechanical pump and just run an electric pump with a return regulator.

Just the fact that the pump is in the block, heating the fuel is reason enough to not use one.
 
Newbomb Turk said:
I would just skip the mechanical pump and just run an electric pump with a return regulator.

Just the fact that the pump is in the block, heating the fuel is reason enough to not use one.
Click to expand...

I'd agree but this is mostly a street car and electric pumps that aren't mounted inside the fuel tank are noisy as hell. Ideally I'd run an in-tank pump and bypass the mech pump (and ditch this carb for a Holley DP) but for the time being I just want something I can add into the existing system to give it a little boost.
 
I don't think the issue is pump related, but carry on.
 
I agree with RRR, I think you need to get into some serious trouble shooting of the fuel system and its delivery.
 
I'm pretty sure the "issue" is the carb, it's sensitive to float level and the bowls aren't very big. I've had it since 2016 and since moving from Colorado last year and having to pretty drastically richen it up for the change to sea-level air the fuel system can just barely keep up. I never had this kind of issue back in CO when the power and fuel demand was substantially lower. I've wanted to swap to a DP-style Holley for a while because this Street Demon just isn't very tunable and not as well suited to hotter engines, I'd say mine is on the border (ported RPM heads and port-matched RPM intake, 222 @ .050" cam).

Engine Masters did a test of this carb in a new-style "street carb" shootout and also found that it leaned out slightly at higher RPMs. I once also talked to a guy at a race/show event who worked at a performance shop in TX and explained how these carbs need extra fuel at higher RPMs, gave me a detailed rundown of the ideal setup... main thing I remember is a rising-rate regulator but idk much about those? Probably easier to just find a good used 750 DP.
 
Do a fuel volume test.
the volume test will tell the tale. You need about half a pound per hp per hour. and fuel weighs about 6 pounds per gallon.
So then, if you really had 450 hp, you would need,
(450 x .5 pound )/6=37.5 gallons per hour.
your pump will need to supply 37.5gallons US/60minutes =.625 gallons per minute, and .625 gallonUS = 80oz.
See what your pump can suck thru that 5/16ths line.
Then do it again but; Open the doggone gascap.
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I had a high-lift 223@050 cam in an 11.3/1 360, with OOTB Edelbrocks, that by it's Trapspeed made 350 hp
But then I installed a bigger fuel line.............
BTW, I loved that cam. Mega torque

IMO
at WOT, the fuel doesn't actually get a chance to pickup much heat from the engine-mounted pump to the intake. ....... but it always starts out hot from idling around.
After that 223 cam dropped lobes, I installed the next bigger cam, 230@050,
Later, I cut a hole in my hood and fed the carb with fresh above the hood air. The car, by it's trapspeed, went to 430hp.
now, you and I both know that one size bigger cam, does not make 80 hp. So how much of that was due to the cold air, and/or how much was due to the 3/8ths fuel-line, is anybody's guess.
But, I can tell you that as soon as I cut that hole in the hood, I was able to upjet from 68/76s to 72/80s, both with the 230* cam.
I run the HO mechanical pump right out of the Direct-Connection catalog, and the line is 3/8ths from pump to the tank, no return line and a honking big EFI filter on the suction side, mounted just in front of the front spring perch on the passenger side. From there, I routed the line inside the frame rail, all the way to the pump. From the pump to the carb is one piece of 3/8ths line no filter, and no filters in the inlets. My thinking was that whatever might get thru the EFI filter, is gonna pass right on thru the engine. I modified the factory pick-up to 3/8ths and installed the matching sock.
This set-up has no percolation issues, and, I run the coolant at a minimum 205*F. The pump and lines were new in about 2002. and the hole in the hood was about 2004 or 05. I'm sorta guessing.
You be the judge.
 
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Don't use 2 pumps!!! Have ONE good one. I tried that with my GLH (2 pumps) and had issues that I chased for a few years until someone pointed out what my problem was. :rolleyes:
 
This is what I’m running with 540hp, 3/8” feed and return lines, QF 850 and a regulator. No issues with heat or maintaining stable fuel pressure, even in CA heat. The only time you’ll hear it is before you start the engine.

Jimmy, thanks for the link I was just about to search for where I got my current one and you posted it! Been about 6 years since I installed mine and wanted to pick up a spare.
 
Thanks guys, I think I'm going to swap the carb first and go from there. I'll refer back to this thread if I still end up needing to upgrade my fuel system.
 
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