5/16" fuel lines

[luey2009]

I just wanted to make sure that I can run the 5/16" fuel lines safely with my 347 stroker motor. there seems to be different opinions on this. my set up is gonna be a 347 stroker, 4brrl carb, mechanical fuel pump,no return line. Can i get some advise on this before i put in the 5/16" lines? -thanks Andy

[luey2009]

If I upgrade to a 3/8" Fuel line do I have to change the fuel pump pickup that came with the kit to a larger size?

[mirose]

I went back and forth on this one too. I have a 347 stroker as well. It seems the 5/16th is just on the edge of where you want to be (from what I gathered) so I bumped it up to the 3/8th (actually used -6 hose which has an I.D. of 3/8). No issues as of now and I used Teflon/braided Stainless flexible tubing the whole way and I am very happy with that.

As for changing the pickup.. I also went with a larger in-tank pump (I have EFI) and had to change some of the adapters for the pickup to convert to -6AN fittings.....so I am sure you will have to do some of this as well depending upon what you plan to do.

Here is a copy of something I found on a mustang forum:


You may use the following as a fuel pump "rule of thumb". Additionally, it is a good idea to give your system a bit of safety cushion.
I always run a pump just a bit larger than I need just for insurance.

For Dead-Head type regulators:

Multiply maximum horsepower by .23 to calculate minimum pump size in "free flow" GPH.
Example: 400 HP x .23 = 91 GPH "free flow"

For Return-Style regulators:

Multiply maximum horsepower by .17 to calculate minimum pump size in "free flow" GPH.
Example: 400 HP x .17 = 68 GPH "free flow"

These minimum pump sizes assume that the fuel system is equipped with fuel lines of adequate size. If the fuel lines are too small (or if there are a lot of restrictive fittings in the system) a larger pump may be required to satisfy the fuel demand of the engine. The minimum fuel line size (from the pump to the regulator) is dependent on the horsepower output of the engine (and/or Nitrous system) regardless of the size of the pump.

Use these figures as a fuel line sizing standard:

* Up to 250 HP = 5/16" or -04 AN
* Up to 375 HP = 3/8" or -06 AN
* Up to 700 HP = 1/2" or -08 AN
* Up to 1000 HP = 5/8" or -10 AN
* Up to 1500 HP = 3/4" or -12 AN

If you use a return-style regulator, you will also need a return line from the regulator back to the tank. The size of the return line is dependent on the size of the pump you are using, regardless of the engine's horsepower output. The return line must have limited or NO pressure in it. In most cases, the minimum return line size will match that of the supply line, but a larger return line is sometimes preferred.

Use these ratings to decide your return line sizing based upon fuel pump output:

* Up to 45 GPH = 5/16" or -04 AN
* Up to 90 GPH = 3/8" or -06 AN
* Up to 250 GPH = 1/2" or -08 AN
* Up to 450 GPH = 5/8" or -10 AN
* Up to 900 GPH = 3/4"or -12 AN

I have no idea if this is total B.S. or not, but it sounded good!!! I do see at least one error: 5/16 line is -5 AN not -4...so maybe its total horse-you-know-what. Hope that helps.

Michael

[luey2009]

Mike, did you have to upgrade to a 3/8" fuel pimp pick up for your 3/8" fuel feed lines? and if so, where did you get it from?

[mirose]

Mark at breeze helped me out and sold me what I needed. He knew just what i needed to attach the pickup to my -6 AN Fitting on my braided stainless hose. If I remember right it's a compression fitting to the pickup and then an adapter or two in sequence that got me to my fuel line. Let me know if you need more specifics and I can research it a bit more. - Michael

[luey2009]

thanks Michael I appriciate the help!

[canuck1]

I am not sure where that fuel line size data comes from.

This comes from Holley's instruction manual they send out with many of their EFI systems:

10.1 Fuel Line Sizes
Fuel line size is important with EFI, but there is a tendency to oversize feed lines. A high pressure EFI system does not need the same size lines as a low-pressure carbureted engine. A 3/8" diameter line (-6 AN) line is adequate for engines to at least 750 HP. This is a conservative number. A 1/2" diameter line (-8) line should be used on engines over 750 HP.

I think it is always smart to build in some extra capacity in both the lines and pump, but most EFI systems don't require fire hose size lines to get the job done.

Sean

[mirose]

Originally Posted by canuck1

I am not sure where that fuel line size data comes from.

This comes from Holley's instruction manual they send out with many of their EFI systems:



I think it is always smart to build in some extra capacity in both the lines and pump, but most EFI systems don't require fire hose size lines to get the job done.

Sean

I am not sure either. I found it on the club cobra forums. Looked pretty well thought out but very well may have been opinion. Anyway, the OP is putting a carb in, not EFI, so that would mean he DOES need bigger lines if you believe your Holley info. I happen to think that a little extra capacity isn't a bad idea. We are talking about 1/16th of an inch more. It's not like we are talking about putting 3/4 inch lines in. As we all know many builders chance their minds and upgrade their engines after they start to build, or sometimes even after they are done building! It can't hurt, IMHO to have the lines there.

[canuck1]

Originally Posted by mirose

... I happen to think that a little extra capacity isn't a bad idea. We are talking about 1/16th of an inch more. It's not like we are talking about putting 3/4 inch lines in. As we all know many builders chance their minds and upgrade their engines after they start to build, or sometimes even after they are done building! It can't hurt, IMHO to have the lines there.

I agree.

Sean

[CraigS]

I would go 3/8s just to be safe. It's also a heck of a lot easier to do now than later on a completed car.The other problem is that it's often hard to tell if your supply is marginal. It will only show up under under sustained hard driving and it could cause a lean out that you don't really detect until it's too late.

[luey2009]

Originally Posted by CraigS

I would go 3/8s just to be safe. It's also a heck of a lot easier to do now than later on a completed car.The other problem is thatit's often hard to tell if your supply is marginal. It will only show up under under sustained hard driving and it could cause a lean out that you don't really detect until it's too late.

Craig I ordered 3/8" lines, do I need to upgrade the intank fuel pump pickup that came with the kit? or will it work?