Bypass type fuel systems (Carb)... Thoughts?

I just picked up an Earls 140 fuel pump for the truck and after a bit of research I'm thinking about doing a return style fuel system. Seems like it may have multiple benefits from what I've read. I'm still trying to work out the details though and would like to hear how you guys have your fuel systems setup, what specific components, line size, etc. you are using and what the respective ET or HP is. As always, appreciate the help. Feel free to post pics. -Trent

Before I went EFI, I used a low pressure return regulator, 3/8 supply 3/8 return, worked great

I followed the manufacturer's instructions , even though they didn't make a ton of sense to me. B.G. HR 240 pump.
-8 from tank to carbs , -8 to bypass regulator , which is past the carburetor and -10 return to the tank.
The pressure stays right where daddy likes it under load and not that I am at a level where it will make a big difference , but the fuel is always tank temperature , and doesn't head up sitting in the under hood area.
I insulated the lines where they are near potential heat sources , and I did that with my last deal that didn't use a return.
I never had a problem with re-starts or boiling fuel in that one either.

I used to run the Aeromotive 11203 "street rod" pump w/ -8 line from a sumped stock tank to a deadhead regulator. It worked great running mid 9s at 140 mph, but on the street I had vapor lock issues w/ pump gas. At the track I never had any issues w/ vaporlocking, just had issues driving it on the street.

Switched to the bigger Aeromotive A1000 pump w/ a -10 feed and used my old -8 line for the return. Obviously I used the matching Aeromotive return style regulator up at the carb. Didn't run any faster (didn't expect it to) but it did help a LOT w/ the vapor locking issues I was having before.
I've since added a fuel log w/ a total of 3 regulators for the nitrous. Very happy w/ this system.

I'm considering seriously changing mine from a dead-head to a bypass setup, but haven't nailed down the specifics. The way I've heard my Mallory 140 complain when the engine's been forced to idle for extended periods tells me something needs to change. A way to adjust the fuel pump speed to engine RPM / demand would be helpful, too, even w/ a dead-head regulator.

[quote=tubtar]I followed the manufacturer's instructions , even though they didn't make a ton of sense to me. B.G. HR 240 pump.
-8 from tank to carbs , -8 to bypass regulator , which is past the carburetor and -10 return to the tank.

This is what I use as well, except I replaced the BG pump with a Mallory 250 when it locked up at the strip. This arrangement works just fine for me with street / strip use.

Mark

I am sold on return style fuel systems for my usage/application (mostly street, track only when I can squeeze it in).

My Garbage currently makes just shy of 500 to the rear wheels, I'm using Mallory branded pump and regulator with
-8 AN braided hose to and from the regulator, -6 to the bowls. Sorry I don't remember the part numbers.
-10 would be preferable per the pump manufacturer but I didn't want to deal with the additional bulk.

I first prototyped it with the cheap Carter of the day/late 80s (4594? whatever the direct connection book said to get, is what I had),
I ran it deadheaded for a long time but then tried a rubber return line with about a .060" restrictor.
The difference was noticeable, the pump did not heat up anywhere near as badly as before on the street.

The next version had an upgraded pump and regulator but at first, I could only afford hard lines at the time.
I made the lines best as I could. I was quite shocked to find that on a 90+ degree day the fuel lines would feel cool to the touch, enough to "sweat".

Later I upgraded the electrical system to include a fuel pump relay instead of direct switch.
By then, I had used the system enough to be 100% sold on it.
After that the braided hose and all that came into the picture.

Do you need all this? I think a really simple deadheaded system is just fine for an awful lot of drag cars. Especially ones that show up
to the track on a trailer, where nothing is really allowed to get hot for any length of time.
(That's not what I have).

I assume you're describing figure #3 as referenced below. It doesn't make much sense to me either so I may call Holley tomorrow and ask a few questions about it for clarification unless it comes to me pretty quick. I'm also trying to understand why some systems utilize a larger return than the supply while others run the same or even smaller with a restrictor. I was original leaning towards an Earls 12847ERL regulator but need to do more research on all the details before I pull the trigger on one. In all honesty, I'm not sure that the buy in cost on that particular regulator makes a lot of sense unless I'm just set on having all Earls components. There's probably a better choice one way or the other. Just need to decide what that is.

Im 8 up 10 back to tank with reg after the carb. Mallory 140 with their regulator. Been running this setup on past 2 cars for 15 years. No other way I would do it

While you have a Holley tech on the phone, ask them why they still recommend power valves open at half the idle vacuum.

This is the correct way to do it. Return should be larger than the feed , reg before the carb .
This is how mine is done and as prescribed Magna.

Either figure 2 or figure 3 will work. We use both styles depending on what fits the best. Both styles seem to work just fine on the typical performance car. I've used both styles for EFI also.

For years and years i ran a blue, then when it became a 9 second car a Holley Black pump deadheaded.
Drove it a ton on the street and raced it a bunch at the track. Never a peep under any circumstances.
I finally cave to peer pressure( some of it on here... lol) and switched to a much bigger system that also was return style.
The car ran identically to how it did before.
Whatever you decide to do, if the car gets street driven, make sure whatever pump you run is designed for continuous duty use.
That isnt always the case. Check.

I used the Morosso log fuel regulator. I liked that the fuel was unrestricted to the carb inlets. once it reached 8 pounds the relief opened and the excess went back to tank (front mounted cell) steady circulating till full throttle.

This is the approach that I had in mind.

Makes no sense to me why the return line would need to be bigger than the feed line; there's already going to be a reduction in volume from filling the carb, so having it the same size should be sufficient... IMO.

EDIT: Not sure of the manufacturer, but here's another schematic that's similar to what I posted above.

Return line should be bigger than feed line so the the regulator does its job. An equal size return line can cause x amount of pressure by itself rendering the regulator useless

Placing the regulator after the carb insures fresh cool fuel at all times to the carb

Its not about the fuel system making the car faster. Its about the life of the pump. Not having a single fuel related issue when its 1 million degrees outside. There is always someone from Michigan that says its a worthless upgrade. But down in the south it's the best thing you can possibly spend an extra $100 on

I now like and use the Magnafiuel pumps on all my cars that need a good high-volume fuel system, I plumb them as instructed and have no more problems with fuel delivery
No need for a return line from the front of the car also

I've ran Holley Blue pumps and have the billet black on it now and have never had any issues in hot weather, yes it gets hot here in KY too. I had a junk Magnafuel 275 that was plumbed like the diagram Brad posted. It lasted about two years before a bearing locked up. After a complete rebuild it started leaking the first summer, junk.

That system should work just fine on most cars. I think that you could even put the regulator in the trunk next to the fuel cell and dead head the pressure line to the carbs and have it work okay. That is the way my Duster is setup and it works. Some people don't like the long dead head section but it is under pressure so it should be fine. Most OEM cars are that way, even the high performance ones.

Thats true Andy, BUT they are ALL high pressure EFI, down here in the heat @ 6 to 8 psi for Carb use will have problems.

In my Coronet I purchased a Magnafuel300 for the single fact alone the bypass was at the pump and not the regulator. My bypass line was 18" instead of 18'. No way I'd run two full lengths of fuel line that distance if I didn't have to. Less likely your gonna have a leak, it's cheaper, and even if a regulator pump bypass was better the advantage would be negligible.

I ran this setup till the car sold, 6.5lbs rock solid.

Yeah Magnafuel recommends a fuel system like Brad posted with a short return line and then a long dead head pressure line to the engine. They also recommend a smaller line on the bypass than on the feed line. Here is a link to their instructions. http://www.magnafuel.com/assets/300-instructions.pdf

My Mallory 140 doesn't have a built-in bypass like some of the other pumps do. If I decide to set up a return line in the style shown in those diagrams, would adding a bypass regulator right after the pump (in addition to the dead-head regulator at the carburetor) function the same way? I think it would, but maybe I'm overlooking something about how the bypassed versions are designed.

This is exactly what is on the current car. Flawless. Car makes north of 900. Previous car had a Mallory 140 and a Mallory return style regulator at the carbs. 8 in 8 out. It was constantly over pressure at idle no matter what adjustment was made. Same carbs with both systems. Finally added a second bypass like pictured in the trunk at the tank. We even bored the return larger in the regulator, Lines are bulky, more weight, more $ in fittings. Wasn't worth it.
Doug

the problem with the regulator at the pump it doesn't circulate the fuel up near the carburetor. The magnafuel pump has a return at the pump but that didn't help with the fuel getting to hot and boiling. I put a return regulator at the fuel log and its been good ever sense

My fuel line runs up the inside of the frame tie, then it crosses and goes outside and into the passengers wheel well. It's away from the headers and I've never had any heat soak problems.

I can't imagine temp is a problem unless you're dealing with a really small tank. I never had any temp issues with my setup (I think it was 10 gallons), hot lapping, in August. Even still, how hot does the fuel need to get before it causes a timing issue?

the problem isn't at the track its running pump gas on the street sitting in traffic. the ethanol boils at like 175. biggest problem I noticed if you stopped for a few minutes and went back out and it heat soaked is when it would act up.

I fully didnt expect it to go faster, i figured the black pump gave it all the fuel,it needed in the first place. Just made the mistake of listening to others tell me my system was inadequate and should be upgraded
It never failed, the pump still worked fine after years of use when i upgraded( foolishly)
It gets hot up here too. 90 degree days arent a rarity. Hot is hot. Most racing and street driving was done in the summertime.

Why does the fuel get hot? Routing or pump stalling? Pump stall is alleviated by the rear bypass or running the pump on a PWM signal. Routing is easy enough to cure. You will see even most OEM's have eliminated tank return.
Doug

Never had any issues with the current setup, even in peak summer heat. I'm thinking only in terms of keeping the pump "happy."

the problem isn't the pump, its the heat under the hood. oem cars are fuel injected so the fuel is under high pressure there isn't a problem with it. as soon as I tried non ethanol gas it was fine or cam 2. the problem is the ethanol. winter ethanol is worse than summer blends. I know a few people having the same issues

Im sure you realize that efi does not have the same problems as the increased pressure raises the boiling point

And Im not sure how many guys here have ever driven their cars for 8 hours straight across states.

Yes, it gets somewhat warm in Michigan. I drove my barracuda there, i also drove to TX, LA, OK, MO,KS,TN,OH,AR,IN,IL,KY to name a few

I drove my '69 383 Super Bee with 4.10s from Virginia to Oregon and back... about 5 days of all-day driving each way. But that was in the late '70s, so it's probably not what you're talking about.

The Challenger has done multiple 4-hour drives at 65 to & from NJ, which probably is.

Oh, but you mean in THIS decade. /

My buddy has a single holley blue pump and 3/8 line dead-headed. Car runs 9.80's, best in the 60's. Been on the car since I've known him. Early 90's. Just some consideration. I run a BG400 in my car #8 return, that's fitting size that comes on the pump, #10 to the reg at the carb. My best was only 9.70's We both have never had any fuel issues. Guess who system/layout cost more. I believe though mine would support a switch to alcohol.

Eddie Miller went 8.50s in 06 and 7.9x in 08 with 2 holley blue pumps. And one was dangling only held in place by the fuel line

I didn't realize you were so much older than me. Jeez, i invited you to be my copilot. Not sure you would have been any good to me

I'm deaf, blind, overweight, going bald, and turned 60 last year... sounds like the perfect combination of traits for a co-pilot to me.

Forgot one thing had to do over, this was my system. The needle and seat are the biggest restrictions # 6-8 everywhere else. Ran 5.50 @125 with a holly blue pump and cell in the front. 499 Indy, dominator, pg. @125 mph, I don’t think it was running lean

Putting a filter directly after the pump is a no no cos the pump is already filtered by the 100 micron pre filter. The 40 or whatever size after filter needs to be close to the carb to catch the fuel line material that slowly breaks down or any crap in general in the system.......

The magnaflow setup seems like the best design for the type of application that you are talking about. (assuming a person is still willing to use a carb for a car that is driven a lot)
The magnaflow has a return line off the pump so the fuel line to the front of the car is running at 30 psi. 30 psi is high enough that there will not be any issue with vapor lock. Then there is a small non-return style regulator near the carb that drops the pressure to 6 psi. That final length of 6 psi line should be short enough that it doesn't vapor lock. My guess is that type of setup would be able to handle most any type of fuel and weather conditions.

Come on Ray you've been here it doesn't get that hot in Illinois. Lol Gateway I believe can be almost as hot as hot can get.

I have that system its not really vapor lock. the fuel is actually boiling right out of the carburetor and yes I have a wooden spacer. I did many different tests with it.and the ethanol is the key problem any non ethanol was fine. I could let the car run in the drive way and once the car got warm which sometimes the engine wouldn't be over 175 and I would start missing and pop the hood and you would see it first start spitting out the squirters then it would start over flowing out the vent tubes like a volcano. if you pop the hood quick enough it would get the heat off the carburetor and would run fine. Since I put it the return in it has helped 100 %

Well, you wouldn't have had to worry about my fuel system

MAGNAFUEL and that's what I run and have on the street for many years and yes, even w/a nasty hard to tune carb and it's 1200 cfm to boot. No vapor lock even w/91 pump junk and I even get decent mileage if I cruise on the primaries and funny enuff, so does Ray Meyers who won Drag Week and even got up to 16 mpg's w/that nasty old 1050 Dominator thingy........

Aeromotive doesn't agree w/ this. Not saying one is better than the other, just pointing this out. When I designed my system I called them to make sure I was on the right track. They recommended a -10 feed and -8 return.

On the street you need the fuel circulating from the carb back to the tank. The short returns from the bigger pumps back at the tank won't work real well on the street. That long stretch of fuel the length of the car needs to circulate to keep it cool.

Yep, and I tried the return deal on their hot rod pump and it couldn't keep up and went a best of 9.98 then switched to the MAGNAFUEL 300 and went 9.79......

I don't think the Aeromotive 11203 hot rod/street rod pump flows enough fuel to feed a 9 sec car w/ a return style system. It works fine deadheaded though. I went 9.54 at 140+ mph w/ that pump and a single -8 line deadheaded.

Not likely my Mallory 140 can support a return setup, either. Guess I'll leave it as it is until I consider a fuel system upgrade in the future.

Agree but it said it supportes x amount of power deadheaded and x amount more iirc returned back to the tank.....

Says it supports 750 hp carbureted on gasoline. Don't see anything saying the "horsepower rating" changes whether deadhead or return style. It fed my car just fine, so there's no reason it shouldn't have fed your car easily unless you have a restriction somewhere else in your system...OR, if like I said earlier, a return style system just requires a larger pump to keep up w/ demand.

Just because you have a return style regulator, does not mean you are always returning fuel. I see no reason why a pump that is maxed out on a dead head regulator would not supply the engine with the same amount of fuel with a return style regulator.

If the return regulator stops returning it's because the fuel pressure has dropped below the setting, & that means the pump volume is to low.

Yes. In other words.... maxed out.
So regulator style would supply the same amount of fuel to the engine.

I read something that said it would support like 700+ hp deadheaded and like 900 w/a return but I don't remember exactly where I read that and it was years ago..........Hell, maybe I was drunk.....

And he was also pumping methanol from an alternative source 😏

Attention in the pits

Fuel pump must have the internal bypass disabled to run bypass regulator

On a mallory 140, there is a screw with jam nut, you remove the pressure spring just like a bb mopar oil pump and put in a solid spacer so the pump is on kill at all times

No he wasnt. I was his copilot. I dont know where that comes from

I was pitted next to you In 2006. Your windshield washer bottle seemed awfully important to be filled between rounds. “direct port water injection nozzles”😂
I was also the guy that gave you the hose you needed to continue to next round.
Don’t worry, I won’t tell anybody.

That was at the Pump Gas Drags. Yes, he used that because he was spraying and running pump gas. At DW we put race fuel in but he still only had the 2 old holley blues in his car

could one old holley blue pump support 550hp with a return style regulator ?
sorry if this is a jack, but it does pertain to return style regulators. [i think]

Yes I did it, tank was in the front of car pushing back, 800 hp. Learned this from two guys running dragsters, running 600+ cu in chevys. That old test of how fast a fuel pump can fill a gallon can relates for rear tanks (overcoming g forces and selling high dollar fuel pumps). (Gas is heavy) where does all the junk in your car go when you nail it?

... 'cuz I'd like to hear more about what size (GPH?) pump people think is necessary to set up an effective street/strip fuel system having a bypass/return deal and supporting maybe 700 HP. Thanks - Brad

The 255LPH pump I used was BARELY good for 600 HP @ 6psi ,,the 400 LPH would work for 700 hp. this is an intank EFI pump I was using at 6psi on a carb & return, & as I learned from Dwayne, you have to do a Volume test @ the pressure that is going to be set at. going through the fuel line & filter that is on the car.

I'm really not sure what GPH the Aeromotive A1000 pump flows, but I'm sold on it. It's "rated" to feed 1500 hp NA on gas. It's one of the more popular pumps on fast street driven cars. Been running mine since 2011 I think and it's been flawless.

I did fuel flow tests on my old pump gas Duster due to not being able to jet it up rich enough to slow down the MPH in the 1/4 mile. I had a Magnafuel 275 (suppose to feed 750HP)pump on the car and bought their 300 pump that was rated at 900 HP, my moto had a six pack set up on it so I flowed the pumps with all three flex lines into a five gallon plastic fuel jug for 10 seconds three times on the 275 pump first and then the 300 pump after swapping them out, no noticeable differences in the flow
I call Magnafuel the next morning and told them what I had tested and they told me that I needed to either do the tests with the fuel bowls attached to the lines or put a restrictor in the lines to load the pumps, don't test unrestricted. I decided to hook one line back to a carb and redid the flow test three time, it gain over 40 % flow increase through two lines on those three tests
I ended up finding out that the 10 micron fuel filter I had mounted between my gas tank and the fuel pumps was restricting the fuel flow into the pumps
I ended up putting the 275 pump back on the car and it worked fine plumb like Magnafuel said to plumb it
Sometimes we need help on figuring things out, huh