TL:DR: Hard lines or braided hose for full fuel system revamp?
Ok... Long winded backstory. I have an early 3rd gen Camaro (Carb/mechanical pump SBC) and fuel delivery has always been an issue for me. Lots of bogging and it barely wants to run at anything less than a half tank. Add to that covid and being a college student has pretty much shifted the project to the back burner. But this year she is becoming a priority again. In the distant future there will be an LS swap but I want to get her solid and on the road before that.
the plan is to replace the entire fuel system. Everything. I already have the tank, an Aeromotive Stealth unit with an electric pump that should feed any engine I drop in here. It fits in the stock location but has AN-6 fittings on it as opposed to the stock hard lines.
So I will have to run braided hose with AN fittings down to rocker area where the stock hardlines sit (The hardlines will also be replaced with new stainless ones)
So the question is... should I bother replacing the hardlines and adapting them for AN-6 hoses on both ends or should I just run a braided line the full length of the car? Cost seems about the same either way, but the full braided seems like at least 4 fewer couplings which in my mind means 4 fewer points of failure.
Am I overthinking this? Am I overlooking something?
I would use hardlines as much as possible.
They make compression fittings for hard lines to adapt to male and fittings at the ends, which is what im using on multiple efi cars. Then I'm using ptfe lined flex hose where needed.
Im a fan of the least amount od flexible stuff possible in a fuel system.
I prefer hard line too, with just enough hose for areas needed to handle vibration. Hose wears out much faster.
The hose does wear out.
Also, AN6 will not support ALL oh the hp me thinks.
I am not sure what the limit is, but I've seen AN8 above about 400hp.
The stock hardlines are the same ID as AN-6. (In response to other posts, I've made over 1000hp with 3/8" fuel line)
Personally, long runs of anything flexible under the car give me heebie-jeebies unless you can support it every foot or so. I can picture it getting snagged by a branch or small tire gator or other road debris and getting ripped out.
With that fuel pump, you absolutely will need to run a separate high capacity cable and relay, mount the relay at the back of the car and control it with the old fuel pump wiring. I usually just ran 10ga because we kept a lot of it around.
There is also a very strong chance that you will need to upgrade your fuel pressure regulator to prevent you from having overpressure at idle and low load. Even a 340 may cause you to have 90psi at idle because the regulator can't flow enough to bleed off enough fuel to drop the pressure, depending on the regulator. (LTI seemed to be fine with a single 340, the Corvette filter/regulators however are not)
I say single, because one 340 isn't enough sometimes. Sometimes for best headroom you want to run a secondary controlled by a boost switch or the engine computer.
Was fine with 3/8" line 
Rereading your original issues, I didn't initially see "carbureted". Budget another 200 or so for a carb friendly regulator (that will probably fail a lot or have floating pressure anyway, have never had luck with any bypass type low pressure regulators), and you will also have to run a return line, so in THIS case you may as well use the existing hardline as the return and run whatever you want as a new feed.
I think your fuel pickup has a rust hole in it, myself, but I get the idea of future proofing, especially when dropping the tank is so "fun". It's not too bad on a lift, if you have a lift...
For what it's worth to step EFI fuel pressure down to carve a friendly pressure, I've bought the cheap eBay bypass regulators and drilled out the orifice under the check ball a few steps up until it was adjustable low enough and Rocksteady for fuel pressure. Got a few of them running that way and have been for a long time
Always hard line for as much as possible. Way more durable, and not affected by hydrocarbons like the plastics and rubbers in flex line. Also, once you secure a hard line to the car, it moves almost zero. Even if you secure a braided line every 6 inches, it will vibe and shake and eventually fail.
For my last fuel system I did about 12" of braided from the tank to a bulkhead fitting on the frame, then hardline all the way up to the front and another 8" section from the frame to the mechanical fuel pump. I did a hard line from the pump to the carb because vibration reasons.
Oh... to add. You probably know this, but AN sizes are roughly in 16ths of an inch, so -6AN is equivalent to 3/8". That should help you figure out if you need 6an or 8an based on your HP
Pete. (l33t FS) said:
The stock hardlines are the same ID as AN-6. (In response to other posts, I've made over 1000hp with 3/8" fuel line)
Personally, long runs of anything flexible under the car give me heebie-jeebies unless you can support it every foot or so. I can picture it getting snagged by a branch or small tire gator or other road debris and getting ripped out.
With that fuel pump, you absolutely will need to run a separate high capacity cable and relay, mount the relay at the back of the car and control it with the old fuel pump wiring. I usually just ran 10ga because we kept a lot of it around.
There is also a very strong chance that you will need to upgrade your fuel pressure regulator to prevent you from having overpressure at idle and low load. Even a 340 may cause you to have 90psi at idle because the regulator can't flow enough to bleed off enough fuel to drop the pressure, depending on the regulator. (LTI seemed to be fine with a single 340, the Corvette filter/regulators however are not)
I say single, because one 340 isn't enough sometimes. Sometimes for best headroom you want to run a secondary controlled by a boost switch or the engine computer.
Was fine with 3/8" line
Thank you! I knew somebody with 1st hand knowledge would jump in.
