[Craig Hendrickson]

Originally Posted by Skip Fix

Looks like -10 might be needed with this pump -or just always be WOT

I forgot to mention in my posts above that I used 3/8" (-8) feed and 1/2" (-10) return on my "TurboForce Revival" Firebird 400 project car. Of course a blow-thru turbo situation has different fuel pressure requirements that an N/A drag car.

As a non-Pontiac aside, my current project, a 1956 Packard "Panther", "What if?" car is a restomod with a hopped up Packard 374CID V-8 (2x4 intake, HC-01 size hyd cam and headers), and should put out about 400HP. However, where I live it can be 115F in the summer time and there's a long grade from 2,700ft to 5,300ft to get over the mountain pass to Las Vegas. Therefore, fuel vapor lock is a problem in that situation, as is driving in stop-go traffic in Las Vegas at the same temperature with A/C running and probably 130F asphalt road temperature. This is exacerbated by the 10% ethanol in the gas we can get out here since ethanol has a lower vapor pressure than gasoline. All these conditions being considered, that's why I duplicated the fuel pump, fuel feed, regulator and fuel return sizes from my TurboForce bird onto my Panther. Just another situation to consider on a non-drag, but high performance car that is not FI.

[69Goat1]

Originally Posted by Craig Hendrickson

I forgot to mention in my posts above that I used 3/8" (-8) feed and 1/2" (-10) return on my "TurboForce Revival" Firebird 400 project car. Of course a blow-thru turbo situation has different fuel pressure requirements that an N/A drag car.

As a non-Pontiac aside, my current project, a 1956 Packard "Panther", "What if?" car is a restomod with a hopped up Packard 374CID V-8 (2x4 intake, HC-01 size hyd cam and headers), and should put out about 400HP. However, where I live it can be 115F in the summer time and there's a long grade from 2,700ft to 5,300ft to get over the mountain pass to Las Vegas. Therefore, fuel vapor lock is a problem in that situation, as is driving in stop-go traffic in Las Vegas at the same temperature with A/C running and probably 130F asphalt road temperature. This is exacerbated by the 10% ethanol in the gas we can get out here since ethanol has a lower vapor pressure than gasoline. All these conditions being considered, that's why I duplicated the fuel pump, fuel feed, regulator and fuel return sizes from my TurboForce bird onto my Panther. Just another situation to consider on a non-drag, but high performance car that is not FI.

-6 would be 6/16's or 3/8"...

-8 is 8/16's or 1/2"...

-10 would be 10/16's or 5/8"...

[455firebird1969]

AN (Army/Navy) -8 hose is equal to a 1/2" tube. Tubing is measured by the outside diameter. Depending on the wall thickness, the inside diameter is smaller, so a AN -8 hose is less than 1/2".

[69Goat1]

Originally Posted by 455firebird1969

AN (Army/Navy) -8 hose is equal to a 1/2" tube. Tubing is measured by the outside diameter. Depending on the wall thickness, the inside diameter is smaller, so a AN -8 hose is less than 1/2".

Take a really thick tube to make -8 to equal 3/8's...

[BruceWilkie]

Originally Posted by 69Goat1

Take a really thick tube to make -8 to equal 3/8's...

Yeah...pipe which is also measured in ID. 3/8 iron pipe is approx 1/2" OD iirc.

Cheap AN fittings can also have much smaller ID than the size they should be.

[lust4speed]

-8AN is usually listed with an inside diameter of .430" whether tubing or hose, and that's a little less than half way between 3/8" and 1/2". (.375" & .500"). Throw in some of those more restrictive -AN fitting inside diameters and a few bends and we're close to the flow of the smaller diameter.

[johnta1]

I think you guys are stressing too much?

[Tom Vaught]

Originally Posted by lust4speed

I'm running the Malory 250 pump and large regulator. First installed a -8 hose back to the tank. With the regulator fully open the system had 8-1/2 pounds residual pressure. Went to the -10 hose and open regulator pressure dropped to 2-1/2 pounds. Both the -8 and -10 had the same smooth route back to the tank.

As said above, the problem is at idle where basically all the fuel is being returned to the tank.

Good Post Mick!

What you are really after at the end of the day is proper fuel pressure and fuel flow to the engine under all conditions not just maximum HP conditions.

If you can't set the fuel pressure properly to 6 psi because the return line is too small and even with the adjustment screw is backed off the pressure still reads 8.5 psi, you have a problem. Course I have seen people BS on that deal with "It won't make a difference" but a Holley guy will tell you otherwise. With the bigger line and the lower fuel pressure at idle NOW you can adjust the pressure screw to give you 6 psi fuel pressure at the needles and seats as Holley would like to see.

Some pumps just move too much fuel for the average fuel return line diameter on typical installations.

Tom V.

[Skip Fix]

Was under the car a little yesterday with -10.man that stuff looks big!

[NO67GTO]

That's what she said. 😉

Sent from my XT1254 using Tapatalk

[johnta1]

Are you planning on running all braided hose to the back of the car?

[Skip Fix]

Yes I have the -8 in TPFE so it is a little smaller. Can't find -10 in it and snaking the rubber past subframe connectors and potential tailpipes will be a job.

Is there aluminum -10 ?

[69Goat1]

Originally Posted by Skip Fix

Yes I have the -8 in TPFE so it is a little smaller. Can't find -10 in it and snaking the rubber past subframe connectors and potential tailpipes will be a job.

Is there aluminum -10 ?

Yes...5/8 aluminum is available. I ran it on my other GTO for a return...

[johnta1]

This link may be useful:

Fuelish Tendencies

[Gary H]

On my car I have a VoluMax Holley white pump rated at 250 gpm. It has a #10 outlet and a #8 return opening in the billet base. I contacted Holley tech and they said to run the return from the pump back to the tank, not needed from the regulator. And, that # 8 return is fine since it has a much shorter run. Seems strange that they would make the pump with a smaller return opening if it needed the same size as the supply, as most are suggesting.

[NO67GTO]

Originally Posted by johnta1

This link may be useful:

Fuelish Tendencies

Great read. Thanks for posting. Hopefully my new fuel system will b capable this time around. I blew a brand new motor from running out of fuel.

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[Skip Fix]

John good article there. They have my 250 gph as at the max for -8 return, and my 695 HP close to the max for -8 feed.

Also showed a second dead head regulator at the carb after a return regulator on the drag system-interesting.

[Doug Hopkins]

Originally Posted by johnta1

I think you guys are stressing too much?

I think so to. I got out the popcorn.

[Skip Fix]

Well my 78 TA I had to keep morphing the fuel system as it got more HP as it had starvation issues until I ended up with my current system. a 150 HP more motor I want to do it right the first time.

[455firebird1969]

Originally Posted by johnta1

I think you guys are stressing too much?

Stressing? There is some good information is being shared in this thread, especially why a larger return line is the correct way to plumb a fuel system . Additionally, one will understand that fuel hose & tube measured by the AN system is not necessarily ID.