Fuel Regulator before or after the Carburetor
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.
