[BillyGman]

I have a naturally aspirated pump gas 632 CID engine in my car. I don't plan on ever running nitrous oxide in it either. It's an 800 HP engine. I bought a Mallory electric fuel pump that's rated at 250 GPH free flow, and 230 GPH @ 6PSI at 12.5 volts......

the pump has -8AN sized inlet and outlet ports so I was planning on using -8AN fuel lines. But I'm not sure if the -8an line will be enough. But would there really be any greater fuel volume accomplished if I used a -10AN line when the inlet and outlet ports of the fuel pump are only -8AN? BTW, FWIW, the bypass type fuel pressure regulator that I have (which was recommended by Mallory for this pump) has -10AN ports. I should also add that this is a low reving motor, and has a redline of merely 6,000 RPM, so I plan on setting the rev limitier at 6,500 at the most.

 

[10secBu]

My fuel system is all Mallory.

I run two #8 lines from the cell sump to a Comp 500 filter. Out of the Comp 500 filter with a single #10 which goes to the inlet of the Comp 250 pump. #10 out of the pump up to the 4309 3 port return style regulator, then a #10 return back to the tank.

The feed and return MUST be the same size. I tried #10 feed and #8 return and couldn't get the pressure to set down on the regulator. Spoke with Mallory tech and they informed me the fuel was backing up in the return line. I wound up replacing the return with #10 and the problem was solved.

Oh yea, #6 lines from the regulator to the carb fuel bowls.

I suppose #10 was kinda overkill, but I tend to overkill alot of things I build. If I had it to do over again, I'm not sure if I'd do #10 or stay with the #8.

 

[bracketchev1221]

Mine is a #12 out of the tank to the filter and then #10 to the regulator. From there I have 2 #8's to the carb.

 

[70 SS LS-5]

Hey Billy,
Great to hear the project's moving along.
I would use -10. I've tried -8 on some of my milder 540's and 572's, (not using nitrous), and had fuel pressure problems.
My fuel system now is stock tank with sump with -10 from sump to BG5000 filter/BG240HR pump then -10 to engine/regulator, -10 return.
Post some pics of your progress.
:beers:
Mike

 

[Tom Mobley]

for your engine I'd replace the fittings in the pump with #10, inspect the fittings carefully to be sure that they are not necked down on the end that goes into the pump, drill them out if they are. I recommend you personally inspect with your own eyes every fitting in the system. Many AN fittings, especially if they have NPT on one end, are necked down in the NPT section.

 

[BillyGman]

thanks for your replies. I guess I should also try calling Mallory about this stuff. It kinda makes me wonder why they recommend a pressure regulator that has -10AN ports for their pump that has -8AN ports. I also wonder if I do end up using a -8AN line, if it would have any negative effect on the operation of the pressure regulator, since it has -10AN ports.

 

[70 SS LS-5]

thanks for your replies. I guess I should also try calling Mallory about this stuff. It kinda makes me wonder why they recommend a pressure regulator that has -10AN ports for their pump that has -8AN ports. I also wonder if I do end up using a -8AN line, if it would have any negative effect on the operation of the pressure regulator, since it has -10AN ports.

Billy, there's no problem using a -10 fitted regulator with -8 fuel line unless the regulator is not designed for the output of your pump. The problem is that if you use the -8 line you'll have a pressure loss on the top end.
:beers:
mike

 

[BillyGman]

Billy, there's no problem using a -10 fitted regulator with -8 fuel line unless the regulator is not designed for the output of your pump. The problem is that if you use the -8 line you'll have a pressure loss on the top end.
:beers:
mike

I hear ya Mike. I think you're right. Besides that, if I decide to upgrade the pump some day to a more powerful one, the switch will be that much easier since I'll already have the existing -10AN fuel lines in place. BTW, I'm hearing that the braided lines with teflon inside are the best because they don't leak. if anyone knows otherwise, then please chime in on that.

 

[driver]

Not to take away from your post but to this day I have never figured out my crazy fuel problem?My psi goes from 9psi up too 12 psi but don't seem to be causing a problem.Changed gauges three times,two new reg's and two different fuel pumps and still does the same.From the cell is a #8,return is a #10 and going into the carb is a #8 I think.Had a B&G 400 fuel pump and a MAGNA-FLO 500 and it still does the same.

 

[70 SS LS-5]

Not to take away from your post but to this day I have never figured out my crazy fuel problem?My psi goes from 9psi up too 12 psi but don't seem to be causing a problem.Changed gauges three times,two new reg's and two different fuel pumps and still does the same.From the cell is a #8,return is a #10 and going into the carb is a #8 I think.Had a B&G 400 fuel pump and a MAGNA-FLO 500 and it still does the same.

Driver,
What type of gauge do you have?
What type of regulator?
Is your gas tank or gas cap vented?
Mike

 

[driver]

Yes the cell is vented.