Fuel line routing and pressure regulator questions

RestoCreations · #1 (**permalink**) 12-26-2010, 12:06 PM

I've been looking at pictures of Kirkham's and i have a few questions about the fuel line system.
I am going to use the electric pump that is recommended by kirkham. I see that most people have their fuel lines running from the front of the motor and i assume this is because they are using a standard mechanical pump, or am i wrong?

-I have also noticed that there is only one fuel line running into the pressure regulator and it is normally after the dual fuel line that feed the carburetor. I must be misunderstanding the way this system works. I was under the impression that the feed line from the tank ran into the pressure regulator and then out of it and to the carb. However, that is not the case and i do not understand how it regulates pressure when the line runs to the regulator after the carburetor.

Thanks for the help!

Im looking at pictures of this very nice car on ebay currently for reference.
http://cgi.ebay.com/ebaymotors/Repli...5fTrucks#v4-32

FWB · #2 (**permalink**) 12-26-2010, 12:55 PM

tank to pump, pump to regulator to carb. i have my regulator mounted in front of the motor away from the heat of the side pipes and to keep the fuel line inboard of the frame rail. i can then run the line to the carb without having a heat source heating the fuel in the line going to the carb. the fe's fuel log rests on the passenger side of the manifold, it make for a nice clean instalation.

RestoCreations · #3 (**permalink**) 12-26-2010, 01:10 PM

That is the way i have run regulators in the past as well, but if you look at the link above, the Kirkham in the ebay link does not have a line coming out of the regulator and it enters after the fuel log. I dont understand how that works.

Tom Kirkham · #4 (**permalink**) 12-26-2010, 01:29 PM

http://www.malloryperformance.com/pdf/4309.pdf

Note: figure 3A

FWB · #5 (**permalink**) 12-26-2010, 09:32 PM

honestly, i don't understand how it works either, even after seeing the PDF i would think fuel pressure would be uncontrollable, unless the return having less resistance than the needle and seat would make it work. also i have my canister filter between the pump and the regulator.
so.... tank to pump to filter to regulator to fuel log. i use the mallory 140 pump and a holley regulator.

Gaz64 · #6 (**permalink**) 12-26-2010, 10:10 PM

The 4309 is great piece, works as a bypass regulator.

I have two cars with a 4309.

The carburettor receives fuel at a fixed pressure with no inline restriction, unlike an inline regulator.

Set your fuel pressure with the electric pump running and you're done.

FWB · #7 (**permalink**) 12-27-2010, 12:23 AM

understood its a bypass regulator, but the diagram shows me fuel wizzing by the carbs feed tubes at full pump pressure and the regulator is down wind. seems to defy physics to me.
like i said if the regulator has less restriction than the needle and seat then i can grasp the concept. i guess i'm just missing some pertinent information to be able to see how it is feasible. pump pressure is 14 psi... it is 14 psi at the carbs and doesn't look like it stops being 14 psi until it hits the regulator.

just can't come to grips with regulating line pressure after the device you are feeding from a constant pressure before the device, did i just say that?
thats deep......hehehehe

scottj · #8 (**permalink**) 12-27-2010, 05:09 AM

A bypass regulator is a back pressure device. Closing off the regulator increases pressure up stream. The highest pressure in the system is that to which the regulator is set. A dead head regulator is a pressure reducing device. Higher pressure up stream, lower pressure down stream.

vector1 · #9 (**permalink**) 12-27-2010, 05:19 AM

14 psi is the max the electric pump can put out with a plugged line. with an open line there is no pressure correct, nothing to restrict the flow? so the line between the fuel pump and regulator will see whatever restirction the pressure regulator is set for, the return line after the regulator bleeds off the excess pressure which will be nil because of no restrction.

FWB · #10 (**permalink**) 12-27-2010, 10:51 AM

so lets see if i can paraphrase to see if i get this.........this regulator, (a misnomer if this is correct) actually is allowing pressure to be determined by the amount of returning fuel.

simply letting more fuel go back to the tank keeping the line pressure where you need it. more fuel being returned = less pressure
less fuel being returned = more pressure

hmmm, so with my setup dirt gets into my regulator or a line gets pinched i don't get fuel or have WOT starvation.

with this other set up a pinched return line or
dirt gets into that system and fuel gets sprayed all over my hot engine and i'm engulfed in flames being fed at 140 GPM. wow, i want that i think.

i'm beginning to see the light.....or the flames.....

no, but really i do see the advantages of it until you have an accident and that 1 in 10 chance the return line gets obstructed and fuel comes gushing out your vent tubes and you have a richard pryor situation

RestoCreations · #11 (**permalink**) 12-27-2010, 11:08 AM

I dont even see a return line on the car in the link above and that is what caused the mass confusion on my part.

Hotfingrs · #12 (**permalink**) 12-27-2010, 11:28 AM

I always run the regulator after the carb, with a return line. Set the regulator for 7 lbs pressure and the carb will always get that pressure no matter what the driving conditions. With the regulator before the carb, and at WOT, you are limited by the flow the regulator is able to handle. If the regulator can't handle the fuel demand for the engine or carb at WOT, fuel pressure will drop, possibly leaning out the engine. With the regulator after the carb, the carb always gets it's fuel, and the extra is then sent back to the tank.

scottj · #13 (**permalink**) 12-27-2010, 11:34 AM

Quote:

Originally Posted by RestoCreations

I dont even see a return line on the car in the link above and that is what caused the mass confusion on my part.

It's there... hiding behind the throttle linkage in the driver's side photo.

FWB · #14 (**permalink**) 12-27-2010, 11:42 AM

according to the PDF the return is the port under the regulator

FWB · #15 (**permalink**) 12-27-2010, 11:49 AM

i would use this setup hands down on a race car.......on the street it would scare me.
really think about this......when in gods name are you going to need to have that kind of fuel flow for street driving. even on the track it's questionable, i've fed big inch high risers on the dragstrip with crappy blue holley pumps and holley regulators.
it's not like we are john force, competing for the 500,000 dollar purse. more than half our cars wouldn't even pass tech to go that fast to use the fuel.

Z-linkCobra · #16 (**permalink**) 12-27-2010, 12:19 PM

I have to agree with FWB on this one. YOu can only flow so much fuel through a jet in a carb. The needle and seats are desigen to flow more fuel then the carb can flow at wide open throttle. Unless your fuel lines are smaller than your needle and seat....tell me why you need more fuel flow.

Its a supply and demand type senario....the demand will never exceed supply unless your running 1/4" fuel lines....and if you are then you need your head examined...lol.

I like the idea of the down stream regulator....but think its over kill.

Just my 2 cents worth.