Mallory 4305M help

[diabolical1]

Hi All,

I'm finally starting to setup the fuel system on my '87 and I have a question on my fuel pressure regulator. It's a Mallory 4305m
http://www.jegs.com/InstallationInstructions/600/650/650-4305M.pdf

My question is basically about the how to setup my return. As you can see, the regulator itself has it's own return and it MUST remain functional. However it leaves the quandary of how to handle the stock return from the rail.

So do I:

1. Use a "Y" fitting to collect both the rail return and the regulator returns to go back to the tank?

OR

2. Dead end the rail return and use ONLY the regulator return?

Other information that may (or may not) be relevant includes I'm using a -6 AN fittings, but they ultimately are using the stock (-4) hard lines to and from the tank. I'm also running an FD pump.

Thanks for any help and if anyone has any links of photos, please feel free to include them.

1

[infernosg]

Based on the instructions you linked it looks like Option #2 is the way to go. I unfamiliar with this type of FPR but it looks like if you kept the stock return from the fuel rail you'd never be able to build pressure. What was the rationale for picking a FPR that goes before the fuel rail versus one that goes after it?

[diabolical1]

Based on the instructions you linked it looks like Option #2 is the way to go. I unfamiliar with this type of FPR but it looks like if you kept the stock return from the fuel rail you'd never be able to build pressure.

i guess that's the way i'm leaning, but i just wanted to hear from others that may have traveled ahead of me.

What was the rationale for picking a FPR that goes before the fuel rail versus one that goes after it?

the truth? sadly, there was no rationale. :( i bought it a few years ago and basically, i had a budget and a range of operating pressures. this one fit both. i did not realize that it went before the rail until quite some time after i got it, when i started making plans for lines and i read the schematic.