fuel pressure question

[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.

[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

[M Brand 505B]

I’ve been through this twice. Answer is a -12 return line with a return style regulator to lower the pressure enough.

[Dissident]

When it was said the bypass system can be adjusted so that the pressure is low enough that meant as restricted by whatever the carburetro needle(s) and seat(s) will hold.
I hope I have understood the premise and have tried to attach a sketch in respect of the physics of drag racing.
Rgds,
HB2
Dissident

[Dissident]

Well, my sketch that I thought would describe the fuel system situation very well is way too big (some 20K characters vs 600 allowed), so perhaps this is a better way to present some logic about the subject

See posting below for website link That website is worthwhile to learn something about a method how trustworthy firemen train to overcome gravity. Keep in mind that water has a head pressure of 0.43psi per foot while a typical gasoline has a head pressure of 0.33psi per foot.
Some people want to learn how to apply some sound physics to their racer and others don't. Most who study the application of physics and sound engineering principles end up with faster racecars and bigger smiles.
https://www.fireengineering.com/wp-c...icles/document


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

[Dissident]

https://www.fireengineering.com/wp-c...rgeonOct12.pdf
That is the whole link.....Guess I am going to have to have my local grandson school me on how to work postings on this forum. LOL
Enjoy,
HB2
Dissident