Fuel Sizing 427 Boss Block

[wheelindex]

Hi,

Opinions or builds with a 427.

What are people running with a 427 as far as fuel?

6AN/6AN with a 340 pump and Aeromotive regulator/Holley Sniper was my plan, but I can change it. Guessing for power 525-575hp.

is 6AN fine?

Thanks!
JB

[cv2065]

Hi,

Opinions or builds with a 427.

What are people running with a 427 as far as fuel?

6AN/6AN with a 340 pump and Aeromotive regulator/Holley Sniper was my plan, but I can change it. Guessing for power 525-575hp.

is 6AN fine?

Thanks!
JB

For my 427, I ran -8AN braided lines with Aeromotive 340 and X1 regulator, but opinions will vary. I went by this chart from Summit.

https://help.summitracing.com/knowledgebase/article/SR-04879/en-us

[tnt_motorsports]

I did a QFS 340LPH fuel pump and -6 lines. I am running a 427SBF from Smeding Performance with a Sniper 2. I hope to have my first start by Memorial Day!

[Bob Cowan]

-6 would be bare minimum. as long as you are not pushing it hard for extended periods, it will be OK. That being said, there's no reason not to install -8 lines. The cost difference isn't worth worrying about, and the effort is the same.

Go big or go home. :)

[gbranham]

6AN and Walbro GSS340 pump for my Boss 427 with Edelbrock ProFlo4 EFI. Runs great.

Greg

[Jim1855]

427W 540hp
780 cfm 4150, Edelbrock mechanical pump.
3/8 hard lines from the tank with AN-6 where necessary. Bypass regulator and 3/8 return line.
Many dyno runs and track days turning 7,000 when necessary or so inclined.
Never saw a fuel pressure issue.
For the current build with the same 427 I'll run AN-8 PTFE lines for both feed and return. Still with a carb and mechanical pump. As previously indicated AN-8 only cost a little more than AN-6.
Jim

[rich grsc]

The size of the engine doesn't determine fuel line size, HP does. If you you're under 600 hp, AN-6 will be fine.

[wheelindex]

The size of the engine doesn't determine fuel line size, HP does. If you you're under 600 hp, AN-6 will be fine.

On your 331, we are working on another car with a 331. The stock hanger with the 3/8 and 1/4 return, did you use it? We should be 425-440 on our 331.

[Mike.Bray]

You have to be careful here. Typical -6 tube is 0.375 OD x 0.311 ID. The old -6 AN hose was anywhere from 0.330 to 0.370 ID so no restriction between 3/8 tube and -6 hose. But, today's gas has ethanol in it so they've stuffed an inner layer of PTFE in the AN hose reducing it's ID to less than 0.300. For most street engines the -6 PTFE hose is probably okay but if you're pushing 550-600 HP or more moving up to -8 PTFE hose is cheap insurance.

[F500guy]

The size of the engine doesn't determine fuel line size, HP does. If you you're under 600 hp, AN-6 will be fine.

Rich, You think would this be valid with a 6-an suction line with a mechanical fuel pump at the engine? This thread got me thinking about my own install and I can just about find any answer I want on the internet. I know it is fine for the street, hard to stay in the throttle more than a few seconds so only a dyno run would tell the tale if I would starve out later. Just curious, no plan to run out and change anything.

[rich grsc]

That's a good question, and a little more to think about. On an EFI system the fuel is delivered under pressure by the pump in the tank, so frictional loss isn't that big of a deal for such a short distance. On a vacuum pump, (mechanical) friction loss on even a short distance is possible, the longer the lift, the lower the delivery output, so a larger suction line COULD help. As I DON"T do carbs :(, I will say,,,,maybe :confused:

[Mike.Bray]

All of my cars & trucks are on a low carb diet Rich;)

[bobl]

Some things to keep in mind.
Fuel requirements are based on actual HP, not corrected. So, your actual HP is around 10% (or greater) less than what you think.
Fuel line sizing needs to be larger on the suction side of the pump.
An in tank pump can use a smaller fuel line since there is no suction line.
A return line has the most flow at idle, when the engine is consuming the least amount of fuel. if your idle fp is good then the return line is adequate.

[rich grsc]

All of my cars & trucks are on a low carb diet Rich;)
Amen to that

[wheelindex]

You have to be careful here. Typical -6 tube is 0.375 OD x 0.311 ID. The old -6 AN hose was anywhere from 0.330 to 0.370 ID so no restriction between 3/8 tube and -6 hose. But, today's gas has ethanol in it so they've stuffed an inner layer of PTFE in the AN hose reducing it's ID to less than 0.300. For most street engines the -6 PTFE hose is probably okay but if you're pushing 550-600 HP or more moving up to -10 PTFE hose is cheap insurance.

I measured mine right at .33 ID on my Evil Energy hose.

I was planning 550hp range, so 6AN is a hard question of course!

[ggunter]

I have wondered about fuel line size when building anything with an engine and did some research and experiments to validate what I found. Using a Holley 750 double pumper and using the #75 jets that were in it. The jet opening is .082 on a #75 jet. Four of those jets will flow .12 -.13 gallons per minute @ 5 psi (according to Google asking that question). This does not take into account what the power valves will flow, so I used .15 gpm to include them as well. I run #6 fuel line on me car, so I unhooked the fuel line and put it in a graduated container and turned on the pump. I got 1.6 gallons in one minute, @5psi, so it confirmed what I thought huge fuel lines are not necessary for these cars unless you are running power adders like NOS.

[rich grsc]

Your calculations have one flaw, there is no pressure on the fuel flowing through the jets. The fuel in the float bowels are not pressurized, fuel flows by vacuum at the jets.
Here is something else to consider, you get 1.6 gallons per minute of fuel flow at the pump.....at that rate you would run out of fuel in less than 10 minutes of driving :eek:. So, those who say you need AN8 lines and 340 LPM pumps, where is all that fuel going???? No street driven car can burn 2-3 gal fuel per minute that AN8 and large pumps move. I'm from Missouri, show me why. :o

[ggunter]

I agree that fuel through the jets are pulled by vacuum, but they will only flow so much because of the diameter of the jet. My point being is that having enough fuel in the bowls will certainly be obtained by a #6 hose or 3/8 lines @5 psi with any carb in a street application. But anybody that wants to put mega fuel lines on, have at it.

[ggunter]

And to your point, the figures I was using were with 5psi through a jet. With vacuum pulling fuel it will be less than the figures I had.

[rich grsc]

I understand, not disagreeing at all.