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Fuel Pressure Regulator Options for Boost?
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Author:  stop the beast [ Sun Nov 20, 2011 11:12 pm ]
Post subject:  Fuel Pressure Regulator Options for Boost?
Hey All,

I'm lining up parts for a /6 turbo build and I'm leaning toward an Aeromotive 13301 for my setup (3-20 PSI or 20-65 PSI springs). I'll be running a Holley 350 or 500 2bbl and I'm shooting for 10-15 PSI max.

As I understand blowthrough carbs I'll need to have a pressure regulator that can is boost referenced and can regulate my fuel a few pounds higher than my boost pressure. I.e. if the engine is boosted at 15PSI I need to have fuel going into the carb at 18-20 PSI.

Is this correct? Is there a better option for FPRs out there? This one I'm looking at has a higher pressure spring in case I go past 15 PSI but how does the blow through carb respond to such high fuel pressure at vacuum or low boost?

I've seen a lot of guys running the mallory 4309 but that must be for sub 10 PSI boost setups, right?

I'll be running 6AN lines and a single walbro 392.

Thanks.
Author:  Matt Cramer [ Mon Nov 21, 2011 8:53 am ]
Post subject: 
That is correct - if your fuel pressure is below your boost pressure, the boost would blow the fuel back into the return line. You set the base pressure at what it would be for a normal carb and you only get the extra pressure under boost.

The Walbro absolutely requires a bypass regulator, so modifying a cheap Holley deadhead regulator to boost reference it will not work. There's a couple other carbed pressure regulators that you can use, like the SX 15405, but they're all about the same idea.
Author:  stop the beast [ Mon Nov 21, 2011 10:11 am ]
Post subject: 
Quote:
That is correct - if your fuel pressure is below your boost pressure, the boost would blow the fuel back into the return line. You set the base pressure at what it would be for a normal carb and you only get the extra pressure under boost.

The Walbro absolutely requires a bypass regulator, so modifying a cheap Holley deadhead regulator to boost reference it will not work. There's a couple other carbed pressure regulators that you can use, like the SX 15405, but they're all about the same idea.
Thanks.
Author:  Shaker223 [ Tue Nov 22, 2011 5:25 am ]
Post subject:  Re: Fuel Pressure Regulator Options for Boost?
Quote:
I've seen a lot of guys running the mallory 4309 but that must be for sub 10 PSI boost setups, right?

I'll be running 6AN lines and a single walbro 392.

Thanks.
This is the exact setup I've been running for almost 5 years now with no issues and up to 30psi of boost.
Author:  1974duster kev [ Tue Nov 22, 2011 6:27 am ]
Post subject: 
I run the same setup as shaker223 :D

Kev
Author:  stop the beast [ Thu Dec 08, 2011 12:12 pm ]
Post subject:  Re: Fuel Pressure Regulator Options for Boost?
Quote:
Quote:
I've seen a lot of guys running the mallory 4309 but that must be for sub 10 PSI boost setups, right?

I'll be running 6AN lines and a single walbro 392.

Thanks.
This is the exact setup I've been running for almost 5 years now with no issues and up to 30psi of boost.
The 4309 is rated at 3-12 PSI. How do you get the line pressure high enough to overcome 30 PSI of boost?
Author:  terrylittlejohn [ Thu Dec 08, 2011 6:28 pm ]
Post subject: 
i read an artical i mp muscle on a 360 blow through and they ran a mech fuel pump with a boost line ran to the back of the pump to increase fuel pressure as boost went up. don`t know how reliable this is.
Author:  stop the beast [ Fri Dec 09, 2011 1:08 pm ]
Post subject: 
Quote:
i read an artical i mp muscle on a 360 blow through and they ran a mech fuel pump with a boost line ran to the back of the pump to increase fuel pressure as boost went up. don`t know how reliable this is.
I won't need to mess with that.

I have a walbro 392 on the way and I'm running 6an lines, just need to decide on a regulator and would like to save money on this mallory. It sounds like it'll do a lot more than the manufacturer markets it for.
Author:  Matt Cramer [ Mon Dec 12, 2011 9:54 am ]
Post subject:  Re: Fuel Pressure Regulator Options for Boost?
Quote:
Quote:
Quote:
I've seen a lot of guys running the mallory 4309 but that must be for sub 10 PSI boost setups, right?

I'll be running 6AN lines and a single walbro 392.

Thanks.
This is the exact setup I've been running for almost 5 years now with no issues and up to 30psi of boost.
The 4309 is rated at 3-12 PSI. How do you get the line pressure high enough to overcome 30 PSI of boost?
If it has a boost pressure port, that will add 1 psi fuel pressure for every 1 psi boost.
Author:  1974duster kev [ Mon Dec 12, 2011 1:21 pm ]
Post subject: 
Yep the mallory reg is a good piece the only problems I had with it was getting my plugs for the extras holes I didnt use to not seap gas even after i used pipe dope on them. After I tryed a few different plugs though seemed to seal up.

Kev
Author:  stop the beast [ Mon Dec 12, 2011 1:23 pm ]
Post subject:  Re: Fuel Pressure Regulator Options for Boost?
Quote:
Quote:
Quote:
This is the exact setup I've been running for almost 5 years now with no issues and up to 30psi of boost.
The 4309 is rated at 3-12 PSI. How do you get the line pressure high enough to overcome 30 PSI of boost?
If it has a boost pressure port, that will add 1 psi fuel pressure for every 1 psi boost.
Yeah, that all makes sense now. 3-12 PSI is the intial setting. The more you know.
Author:  player1up [ Thu Dec 15, 2011 6:31 am ]
Post subject: 
I have the exact same setup that I plan on installing this weekend.
Mallory 4309
Walbro GSL392
Stock feed line
3/8 return

I'll let you all know how it turns out.

There is one last thing that I'd like some input on.
Where to mount the in-line pump?
There isn't a really good place that is both lower than the pickup and close to the tank.
I'd thought of building some sort of box/hanger thing to hang from the underside of the car, but I just can't seem to come up with something that is like Ah ha! that will be awesome...

Oh, TerryLittleJohn, I tried the boost referenced mech pump thing..works great :P as long as the diaphragm doesn't see more than about 10 psi...as soon as that happens, the pump ceases to function and the car stalls...
Author:  1974duster kev [ Fri Dec 16, 2011 1:22 pm ]
Post subject: 
I mounted my pump on the passenger side frame right in front of the gas tank, and I ran 3/8 hard line feed and return.

Kev
Author:  player1up [ Mon Dec 19, 2011 6:52 am ]
Post subject: 
ok well I didn't get to the turbo install, but I did get the pump mounted and the system seems to work well.
Out of the box, the 4309 regulator was set just above 10 psi. Set it to 7 psi for the holley carb and no leaks! I'm running the electric pump just in front of the rear wheel on the passenger side.
The pump is pretty quite too, not like some of the vids on youtube, but I'm guessing that's because it's regulated so low and it's not working very hard.

So just a recap:
Stock feed line
3/8 return
GSL 392 pump mounted just in front of the rear wheel
4309 Mallory return regulator set at 7 psi

Electric supply is fused from the back of the alternator to feed a relay that gets triggered from the ignition feed. ( so the pump relay is only on when the ign module has power )
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