fuel pressure question

[ss3011]

There has to be some sort of regulator in the fuel pump . Just like a Holley Blue which has a spring that can be shimmed or cut down . Does your pump have a bypass that gets plumbed back to the fuel cell ?

[jamie2370]

Originally Posted by ss3011

There has to be some sort of regulator in the fuel pump . Just like a Holley Blue which has a spring that can be shimmed or cut down . Does your pump have a bypass that gets plumbed back to the fuel cell ?

Yes, I have adjusted it as far as I can. This is off their website

This pump, like all MagnaFuel pumps, is compatible with all racing gasolines and alcohol
fuels. Fuel additives are not recommended and may void the warranty. The MP-4401 and MP4450 have and external by-pass is adjustable from 25 to 35 psi. They come preset at 28 psi.
The PRO STAR 500 Series has enough flow capacity to support 2000 HP on gasoline or 1200
HP on alcohol. All MagnaFuel pumps require a #8 return line and a #8 vent or rollover valve.
Return line and vent must be above the fuel level. The Pro Star 500 series pump is designed to
work with a dead-head style regulator

[Jeff Stout]

Had the exact same problem on 2 cars. Installed a -6 return and problems solved. Went this way in a street car that had a -4 and a car with no return. Solved both cars right down to rock solid 4 lbs. One with quadrajet and one with 700 Holley

[ss3011]

It might be a good idea to stick a big fuel filter on the outlet side of the pump . Reduce the fuel pumps external regulator pressure down to around 15 psi by cutting down the regulator spring a bit at a time .

[bert powell]

I had this same problem with 40 micron filter inline before pump. The new regulators are extremely sensitive, mine is a Magnafuel. They said need another filter before regulator, 10 micron I believe but can find info on their site. Problem solved. If you don't have any filter this very well could be your problem.

[Dan Walcott]

I would suggest buying the total system from one manufacture , pump-filters-regulator. lines and fittings. As for line size, follow their recommendations , supply and return. I don't think you want to try to dead head this system. I installed an Aeromotive system last year. from the fuel cell to the carbs(2). Yes it is pricey, but it works!!

[Dissident]

Something to consider when planning or applying a fuel system of mix and match components. Mismatched components and dirty fuel systems cause a great percentage of the problems folks have to work on. All fuel systems are dirty whether with lines cuttings or old line deterioration. Taking the time and caution for filtering the fuel put into the tank through something so simple as a coffee filter is a natural solution.....cheap and effective.

Fuel systems should be evaluated as a SYSTEM where all the components must work together and that basic thought will get you very close to a best performance package!

The "old tried and true" (sic) Holley regulators will not hold more than about 21-22psi line pressure and at even less than that they have significant pressure creep problems. They also have the greatest "droop" curve when tested. Those things were designed to operate with a 10-12psi system pressure back in the day.The only saving grace is that they are cheap....

A reminder: What you need is flow at pressure where the system pressure before the regulator is opposing the gravity of the vehicle's acceleration. That is if the fuel is in the rear of the vehicle and the carburetor is in the front. It is not the expense of the components that qualify them, but their actual functions that make the best selections.

Regards to All that like this kind of stuff,
HB2
Dissident

[jamie2370]

Originally Posted by Jeff Stout

Had the exact same problem on 2 cars. Installed a -6 return and problems solved. Went this way in a street car that had a -4 and a car with no return. Solved both cars right down to rock solid 4 lbs. One with quadrajet and one with 700 Holley

It has an 8an return line from pump to cell. It is plumbed exactly like magnafuel recommends. I'm gonna put a smaller pump on and see what happens. This pump supports 2000hp lol....

[Jeff Stout]

Originally Posted by jamie2370

It has an 8an return line from pump to cell. It is plumbed exactly like magnafuel recommends. I'm gonna put a smaller pump on and see what happens. This pump supports 2000hp lol....

Sorry didn't read that on original post. I have heard some fast cars using the same size return. -12 in and -12 out.
Also on my Olds wagon I'm Magnafuel 400 with -10 and their regular with no return and only get or down to 7psi. The -6 let me get down to 3 psi but I I raised it to 4.5. I was able to run regular screw out about 4 revolutions after making change.

[bykr]

I had a similar issue with my ProStar 500 pushing thru Holley regs. Magnafuel sells a spring to reduce pressure along with opening up the return orifice to 3/8" helps. Using a Magnafuel reg. for the carb also helped as it would still push thru a little on the Holley regs.