Fuel system question Who is running a return?

ng8264723 · #1 (**permalink**) 07-29-2009, 08:37 AM

I have car 592 and was looking into the mallory bypass regulator. I have an electric pump i my car now. Is the thought to add a mechanical pump and run the car with that and the electric? Or is it sufficient to run the electric solely. I have a single carb 482. Do all late model cars come with the return setup?
thanks
chris

Cobrabill · #2 (**permalink**) 07-29-2009, 08:46 AM

You don't need a mechanical pump.Deadheading(no tie-dye jokes please)an electric pump is never a good idea.
Cool(er) fuel IS always a better idea.You know,density,lesser chance of vapor lock e.t.c.

Carbed or FI-it doesn't matter-a return line is a good idea...and required on a FI motor.

trularin · #3 (**permalink**) 07-29-2009, 08:54 AM

Well, I must confess, I am confused.

My $0.02 worth: Run the electric and bleed the leftovers back to the tank.

Adjust your pressure for what works for your system. I like 5 pounds on my carb.

Just a suggestion.

xlr8or · #4 (**permalink**) 07-29-2009, 09:01 AM

I'm running a return on my car with a carb setup but it's because the fuel cell has a built in pump meant for fuel injection.
If you are running an electric pump that is meant for a carb you don't have to have the return but it certainly wouldn't hurt.

N2VENOM · #5 (**permalink**) 07-29-2009, 09:07 AM

I am running a Holley electric pump with a return to the tank on my Kirkham/Roush 451. I am not sure whey you would also have a mechanical pump? Keep it simple....

Tommy · #6 (**permalink**) 07-29-2009, 09:48 AM

I run a Holley electric fuel pump for my carbed 410 c.i. Windsor. Several years ago I used a pump with an internal pressure regulator and no return line. It worked fine for cruising about, but on a hot summer day at the track I experienced vapor lock at the pump. I disabled the pressure regulator at the pump and plumbed a regulator with a return line just downstream from the pump. That solved the problem.

David Kirkham · #7 (**permalink**) 07-29-2009, 04:14 PM

More and more now we are telling people to run return lines. It seems to fix a whole bunch of problems with vapor lock. Make sure the bypass is AFTER the carb so the carb is aways getting cool fuel.

Running a mechanical...

hmmm

Well, lately we have not been running them. Then again, it is pretty cheap insurance if your electrical pump goes out so you can get home.

David

Cobrabill · #8 (**permalink**) 07-29-2009, 04:37 PM

David,is that "cheap insurance" worth the possiblity of what would happen if the diaphram in the mechanical ruptured?

David Kirkham · #9 (**permalink**) 07-29-2009, 05:10 PM

Quote:

Originally Posted by Cobrabill

David,is that "cheap insurance" worth the possiblity of what would happen if the diaphram in the mechanical ruptured?

If the diaphragm goes bad, the electric pump will still work. It has been a long, long time, however, since I have seen a bad mechanical pump. They are pretty much bullet proof.

David

Cobrabill · #10 (**permalink**) 07-29-2009, 05:12 PM

Quote:

Originally Posted by David Kirkham

If the diaphragm goes bad, the electric pump will still work. It has been a long, long time, however, since I have seen a bad mechanical pump. They are pretty much bullet proof.

David

David-if the diaphram fails(ruptures)the electrtic pump will fill the crankcase with fuel.Like has been said-no need for a mechanical pump.

Great Asp · #11 (**permalink**) 07-29-2009, 07:04 PM

I am running a return line, but have EFI so I need pressure and like cool fuel

If you run a Holley Blue, or Red pump and "can" run a return line, it is only a benefit.

For a carb, you only need 5-7 lbs. Unless it is a full race engine, closer to 5 than 7

E

big-boss · #12 (**permalink**) 07-30-2009, 10:09 AM

I run both as was once recommended by Kirkham. The one electric back at the diff and the std Carter HP/HV on on the engine. I run the return line from a Mollory regulator mounted after the carb. The only big difference I made was I added a 1/2in line from the tank- one size bigger than what came with my roller. I thought since I had to add a new line anyway- bigger is better? Only fuel issue I ever had was: I had to clean the filter three time before I got all the crap out of the tank.

jopper · #13 (**permalink**) 07-30-2009, 11:21 AM

I'm running one of these with a 1/2" feed and 3/8" return. Works great.

http://www.jegs.com/i/Mallory/650/4304M/10002/-1

Terry Stapley · #14 (**permalink**) 07-30-2009, 11:46 AM

Question:

If the electric fuel pump quits working will the mechanical fuel pump pull fuel through the inoperable electirc pump??

franklin · #15 (**permalink**) 07-30-2009, 11:48 AM

I also have the standard Holley Electric pump and have a union fitting where a mechanical pump could go at some point. I am running the same as above with the Mallory Regulator and the return line. I also have the same 482/427 side oiler you are running. My fuel pressure is also set at 5lbs.
Hope that helps,
Todd

trularin · #16 (**permalink**) 07-30-2009, 12:08 PM

I had the bottom of my electric fuel pump appart more than once and I am not sure you could draw enough fluid past the vanes to run the engine. It is an offset concentric with free floating vanes that are "thrown" from the center to the opposite wall.

Not sure you can draw off the holley fuel pump.

PANAVIA · #17 (**permalink**) 08-09-2009, 01:55 AM

BTW: the idea that modern cars use a return line is a misnomer-

- they use more sophisticated computers that pulse the fuel pump signal in relation to the need , like a stepper motor..-- and they INSULATE the fuel line so the fuel does not heat up as much.

as for pumps, I think you have to pick.-- mech-or E'.