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914World.com _ 914World Garage _ Fuel lines

Posted by: spunone Jun 27 2006, 06:55 PM

Installed some 3/8 stainless fuel lines both feed & return.Now after talking to A guy from Aeromotive return line is not big enough if I use there's or mallorys return regulators .Said line not big enough on the return and will flood carbs at Idle Anybody have any ideas .? Besides putting in larger return Line .Thanks

Posted by: Thack Jun 27 2006, 07:18 PM

Use a small fuel pump to feed back into the gas tank?

Posted by: URY914 Jun 27 2006, 07:23 PM

Let me get this right.

You have 3/8" supply and a 3/8" return. And he says you need a bigger return?

Wouldn't there be LESS gas being returned to the tank because some of it is being burnt, right?

I don't use a return line, no wonder my car won't idle.

Posted by: Thack Jun 27 2006, 07:27 PM

Why do you need a return regulator? Is the flow that strong?

Posted by: GeorgeRud Jun 27 2006, 07:34 PM

As long as there's a return and a fuel pressure regulator that hold the carb pressure where it should be, I can't help but think that you're just fine. If you start having trouble with float levels, then the pressure may be too high, but as long as the lines are the same size, you shouldn't have any problems. Mine are about the same on my carbed 2.7.

Posted by: lapuwali Jun 27 2006, 07:55 PM

Note he said their or Mallory's return regulators. It's possible they work depending on a pressure difference between the feed side and the return side, and depend on the feed side having a higher pressure than the return side. With equal sized lines, the pressure will be equal on both sides, so the regulator will either stay shut, or stay open.

Strictly a guess on my part...

Posted by: spunone Jun 27 2006, 09:17 PM

he said supply line is fine but with a return smaller than 1/2 inch you get to much back pressure and the regulator will not operate correct at set pressure

Posted by: tat2dphreak Jun 27 2006, 09:24 PM

umm... carbs don't use a return line.. .at least none I've ever seen... and a 3lb pressure pump(which is all you should have on carbs) wouldn't create enough pressure for a return line anyway... wtf? is this something new? return lines are usually used for FI... where high pressure is sent to the system, and what ever is not used is sent back

do /6s have a return line whereas /4s(carb setup) don't? is that the difference?

Posted by: Aaron Cox Jun 27 2006, 09:31 PM

carbs DO use a return line... if you do it the UBER correct way...

fuel will end up cooler... etc.....

ask brant. he posted the benefits

Posted by: brant Jun 27 2006, 10:16 PM

Thanks for the introduction Aaron...
yep.. I'm the harper..

carbs do use a return line if they are done right and done for maximum HP...

and heck wouldn't it be worth another 5$ to do something right and possibly better.
(go to a race track and see how the top carb guys are plumbed...)

regarding you fuel line dilema..
I think you'll be fine.

why don't you buy a fuel pressure gauge and then "know" for certain.

you can plumb the regulator either before or after and use the guage accordingly.

you should be fine unless you have a Monster!!! pump on it.
I've seen a 906 motor (twin plug 2.0/6L with 46 carbs) run just fine on a 15psi Holley pump with a regulator. If your pump is bigger than that I'd recommend down sizing your pump.

brant

Posted by: Thack Jun 27 2006, 10:19 PM

Unless you have a monster motor, this Mallory unit sounds like it's overkill. How much hp does your motor make? Maybe this return regulator is set up for a loop style, huge carb that needs a lot of fuel. What kind of setup do you have Spunone?

Posted by: spunone Jun 28 2006, 07:29 AM

I'm going to be running a 2316 about a 185 HP not crazy big.Reason for running return cooler fuel = max hp .The pump is not huge it's the regulator that has the problem with the return line .Brant what regulator are you useing and what size return you running? Thanks all

Posted by: brant Jun 28 2006, 08:19 AM

I'm just running a holley regulator (not too impressed with it actually..)
and I'm just using the 2 sizes of brake-line down the center tunnel.

what are those 2 common sizes of brake line?
maybe 5/16 and ?

brant

Posted by: tat2dphreak Jun 28 2006, 03:29 PM

now I'm really confused... carbs generally like warmer fuel than FI, so using the return line to cool the fuel seems counter productive..

how is the setup properly plumbed though? there's not return-out for webers that I've ever seen...

as it is now:

fuel line from tank

________________________________========carb 1
________________________________||
(tank)=(pump)==============="T"
________________________________||
________________________________========carb 2

Posted by: spunone Jun 28 2006, 03:34 PM

Ok Wayne here ya go Tank- Filter -Pump - regulator-carbs .the return line is from the regulator so there a smooth flow at all times .Youcan also use another filter before the carbs

Posted by: tat2dphreak Jun 28 2006, 03:39 PM

ok, I see... my regulator is at the "T" I have filters before the "T" and before the pump... so I just need a different reg. with a return... ok, that's not bad then... still seems redundant though... the regualtor should "regulate" the flow without the return... but I see the point in it now... and it won't make the fuel cooler though... because the return is before the carbs...

Posted by: scottb Jun 28 2006, 04:09 PM

any one have a part number and dealer for a return regulator? i am going to have carbs on my new motor. not a monster, 2056 125hp.

cheers,

scott

Posted by: brant Jun 28 2006, 04:30 PM

Ok...
I finally found the old thread I wanted on the 15th page of my search:

http://www.914world.com/bbs2/index.php?showtopic=43028&hl=
it is..

it actually shows a wonderfully done diagram with 6 different manners to plumb this...

I agree that carbs might like some heat...
when the ambiant is freezing (said sarcastically)

I don't think that in the summer, and after the car has been warmed for a few minutes that heating the fuel is a problem with carbs.

The modern fuels SUCK...
they are MUCH more sensitive to temperature than old style fuels.
in fact at as little as 100F they can start to act up and cause problems
most engine bays are way over that temp in the summer.

I shielded all of my fuel lines in the engine bay for just that reason

brant

Posted by: spunone Jun 28 2006, 05:01 PM

Mallory makes a nice regulator with return as does aeromotive just make sure you buy the one that can go down to 3 1/2 PSI I sure there's others out there make sure you use the right filter before the pump one that won't restrct flow

Posted by: Thack Jun 28 2006, 05:13 PM

I see what you mean now. Are you going to replace the return line or keep it and see what happens. Those high flow pumps really flow some fuel and it might be necessary at idle to return the fuel. I thought only huge carbs like 850cfm needed that kind of setup. Always best to go with manufacturers reccomendations.

Posted by: spunone Jun 28 2006, 05:20 PM

Well I'm going to punch a hole in the top of the gas tank put in a bulk head an 8 fitting and run a new 1/2 " return why not was else is new . Seems every time I start to do something I redo 3 times before I get it done

Posted by: Racer Chris Jun 28 2006, 09:20 PM

I can make a 1/2" line for the tunnel Paul.
I did one as a supply line for someone already, with dash 8 fittings.
I have trouble understanding the need for such a large return line though.

Posted by: URY914 Jun 29 2006, 07:07 AM

Chris,

do you run a return line on your car?

P

Posted by: Racer Chris Jun 29 2006, 07:54 AM

I have never used a return line with carbs.
I guess the fuel pressure regulator Paul is using is as high performance as his engine and needs a Tangerine EVO header.