Fuel Regulator before or after the Carburetor

[cudajames]

Working on fuel pressure.

Doing research I could not find any reason/benefits between regulator placement before or after the carburetor.

It seems that before the carburetor would control the pressure going in. After the carburetor would control back pressure? Why not run regulators before and after?

Thanks for the education

 

[MOPAROFFICIAL]

You're seeing/showing a return system .

*Before the carb...

 

[cudajames]

Sorry ignore that imagine.

 

[MOPAROFFICIAL]

Sorry ignore that imagine.

Lol no worries

 

[pishta]

Either will work on a return system. Put the fuel pressure gauge on the carb and tet each position, youll find they are about the same. Think about a wide open hose back to the tank, the carb will barely see any pressure. tighten the bypass regulator and the carb pressure at the inlets will go up just as though your opening the pressure regulator before the carb.

 

[Bewy]

Makes no difference with a return system. The 'load' [ the carb ] takes what it wants & remainder is returned to tank.

 

[RustyRatRod]

On a return system, I like the regulator after the carburetor, in the return line to act as the return orifice.

 

[Bewy]

Yeah, it doesn't really matter. The return system is like a continuous line with a 'branch' going to the carb & a reg stuck somewhere in the line.

 

[mopardude318]

Following Aeromotive’s recommendations, and Rob ‘Crackedback’, I put the regulator after the carb in both my truck and the Dart. Seems to work pretty good.

 

[cudajames]

Thanks, everyone for the help.


I am continuing to have problems with consistent fuel pressure which has been a problem since the Tanks. Inc in-tank fuel pump was installed. The regulator (holley 12-879) is installed before the carburetor.

I need to continually adjust the pressure up and down to 6 psi. The fuel level in the tank seems to affect the pressure. Low fuel level under 1/2 tank equals lower pressure and 3/4 tank and above equals higher pressure.

I am considering adding a second regulator (holley 12-887) to the return line. My theory is to regulate pressure into and out of the carburetor for greater consistency.

Has anyone else experienced this problem or run fuel pressure regulators before and after the carburetor?

 

[Rat Bastid]

Thanks, everyone for the help.


I am continuing to have problems with consistent fuel pressure which has been a problem since the Tanks. Inc in-tank fuel pump was installed. The regulator (holley 12-879) is installed before the carburetor.

I need to continually adjust the pressure up and down to 6 psi. The fuel level in the tank seems to affect the pressure. Low fuel level under 1/2 tank equals lower pressure and 3/4 tank and above equals higher pressure.

I am considering adding a second regulator (holley 12-887) to the return line. My theory is to regulate pressure into and out of the carburetor for greater consistency.

Has anyone else experienced this problem or run fuel pressure regulators before and after the carburetor?

Two regulators won’t fix the problem.

The problem is the horrible design of that regulator. It’s horrible. The basic design is the same as the poorly designed regulator Holley sold all through the 7o’s, 80’s and 90’s. All they did was add a boost/vacuum reference port.

Technically you could do the same with that early style regulator (I did it as early as 1984 until I scrapped that junk and used a #8 Hilborn high speed bypass instead) by putting the fuel in the outlet side and returning it through the inlet.

Go look at the pictures of the non return style and what you have. They are the same thing, except one is billet with a boost/vacuum reference port. Same junk.

I don’t know what pump you have, but I will say that regulator will barely bypass enough fuel for a Holley blue pump. And it’s marginal for that. They have pressure creep like crazy, they are unstable and the ports and relief valve are just too small for even the blue pump.

That’s the facts of how it is.

Save yourself the grief and aggravation and sell that to some poor sucker who likes the bling. Then buy a Mallory 29388 bypass regulator. Put the bypass BEFORE the carb and send it. No trickeration needed.

Otherwise you will do crazy things like add a second regulator and all that. One good bypass regulator before the carb and be done with it.

 

[cudajames]

Big Thanks @Rat Bastid

I finally made the regulator swap to the Mallory 29388. It wasn't a drop-in for me, I had to find a mounting bracket to modify and many excuses later before I finally installed the regulator a couple of weeks ago. After the initial pressure adjustment, I have not had to touch it. Even at cold starts the pressure is where I set up. So happy