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Fuel line install: Inside or outside the frame rail?

24K views 35 replies 12 participants last post by  BillyGman 
#1 ·
Fellow drag racers, hotrodders, and muscle car enthusiasts, I would like everyone's opinion, viewpoints, and even speculations on this topic. I'll be installing fuel lines in my 70 Chevelle soon. So please help me out.

This will be a street/strip application. More street, but I need it to also pass tech inspections at drag strips once in awhile too without hassles. My power level with this car is in the 800 HP neighborhood, so we definitely aren't talking a factory stock sized fuel line here, and I'm asking everyone politely to please let's not turn this into a debate on fuel line diameter requirements, because that isn't what I need.

I'm not sure what the NHRA rules are regarding fuel line placement.(I only have the 2006 book, and it seems they add new rules every single year) Do they specify if it has to be inside or outside the frame rails? And if they do not specify, then what are the pros and cons of either placement? FWIW, the car is already painted, and the body mounts where all replaced before the body was put back on the frame, and I haven't any intentions of taking the body back off of the frame to install the fuel lines. I've also boxed-in the left hand and right hand frame rails. So if I do place the line inside the frame, I'll need to snake it through. What are your thoughts? Pros and cons? Please help me with your input. Thankyou in advance. BTW, I'll also be installing a return line going back to the fuel cell. So if there aren't any specifics in the rules, I'll need to decide, if I'll want both feed and return lines inside the rail, both outside, or one in and one out.
 
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#2 ·
I don't think there are rules saying it has to be inside or outside the rails.

Inside the rails looks cleaner, but the big downside is you can't see the line to inspect it. Also, if you have to snake it in boxed rails, it won't be easy to secure and might vibrate/rub on something and you wouldn't be able to see it until it started leaking.

I got mine mounted on the inside of the rail near the top, which makes it easy to inspect/replace. If you have the teflon lined stuff, keep everything at least a couple inches away from hot stuff.
 
#3 ·
Point well taken about braided hose fraying if it's placed inside the boxed-in rails, but I was thinking that if I placed it inside, I can get some type of heavy shrink tubing to put around it before I snake it through.
 
#4 ·
I have asked this same question before on a different web site. How I under stand it, is you must have the NEW replacement fuel line shielded "boxed". Along side of the flywheel. As for mounting the line it's self. Sorry I can't help. I used the factory mount locations inside the frame for my NEW line.

You said you have a fuel cell. Did you install a "Firewall (front or rear) .032 inch aluminum or .024 inch steel, extending from side to side of the body and from the top of the engine compartment's upper seal (hood, cowl, or deck) to the bottom of the floor and/or bellypan. Firewall must provide a bulkhead between the engine and/or fuel tank and driver compartment. All holes in firewall must be sealed with aluminum or steel." This is a quote from the '09 NHRA rulebook(page 272). It is written almost identical to IHRA rulebook under general reg's.
 
#5 ·
I have asked this same question before on a different web site. How I under stand it, is you must have the NEW replacement fuel line shielded "boxed". Along side of the flywheel. As for mounting the line it's self. Sorry I can't help. I used the factory mount locations inside the frame for my NEW line.

You said you have a fuel cell. Did you install a "Firewall (front or rear) .032 inch aluminum or .024 inch steel, extending from side to side of the body and from the top of the engine compartment's upper seal (hood, cowl, or deck) to the bottom of the floor and/or bellypan. Firewall must provide a bulkhead between the engine and/or fuel tank and driver compartment. All holes in firewall must be sealed with aluminum or steel." This is a quote from the '09 NHRA rulebook(page 272). It is written almost identical to IHRA rulebook under general reg's.
Thanks for bringing that up. the cell isn't installed yet, but I have one that will be, and I also have sheet metal to install in the trunk. ;)
 
#6 ·
it used to be that if it was a stick car, the fuel line had to run outside the frame where the flywheel was-i actually saw a blown flywheel cut into a frame, so its a wicked hit
to be honest i dont remember anything about autos, but with todays hi stall
converters i would have to look it up-of course, when was the last time any tech guy got down on his hands and knees and looked under a car-even when i had my 903 RWHP Procharged Chevelle, they were more interested if the bat. was properly tied down in the trunk, lol
curious how you get the x member in when you box'ed the frame, did you mod it, since it has to slide into the frame to install-i guess the convertables fit underneath the frame, never looked to see
i'll ask a friend that techs cars, he also does chassis work, he should be up on it
 
#8 ·
when was the last time any tech guy got down on his hands and knees and looked under a car-even when i had my 903 RWHP Procharged Chevelle, they were more interested if the bat. was properly tied down in the trunk, lol
curious how you get the x member in when you box'ed the frame, did you mod it, since it has to slide into the frame to install-i guess the convertables fit underneath the frame, never looked to see
i'll ask a friend that techs cars, he also does chassis work, he should be up on it
That's an interesting point you make about tech guys not often getting down on their hands and knees to inspect race cars. Now that you mention it, they never did for the last car that I raced.

As far as how I got the transmission cross member bolted to the frame rails, there were furhter modifications to the frame that I did besides boxing it in. But I also didn't use the factory cross member either. I was doubtful that the 3.5" diameter exhaust that I have would clear the factory cross member anyway, so I bought, modified, and installed one of these Double hump cross members below from Summit racing, and I had mounting brackets for it welded to the frame....

http://www.summitracing.com/parts/SUM-770308/?rtype=10

 
#11 ·
I have a number of pics I can show you, but I don't want this thread to get too far off topic, so if you want to see them, send me a PM with your e-mail, and I'll send ya some via e-mail.

i have simple 3/8" aluminum line from the pick up to the FP at the motor. its snaked through the from in front of the rear control arm to the motor.
i had a hell of a time getting the small line over the frame at the rear with the body on.
but it wasn't bad from the bell housing area to the front of the car.
i like the cleaner look through the frame, and have less to worry about if you run over something and it comes up under the car.
if you can fit it, run it through the frame.

aaron
Aaron, nice post. Thankyou my friend. :thumbsup:
 
#10 ·
i have simple 3/8" aluminum line from the pick up to the FP at the motor. its snaked through the from in front of the rear control arm to the motor.
i had a hell of a time getting the small line over the frame at the rear with the body on.
but it wasn't bad from the bell housing area to the front of the car.
i like the cleaner look through the frame, and have less to worry about if you run over something and it comes up under the car.
if you can fit it, run it through the frame.

aaron
 
#13 ·
I ran my 1/2" aluminum line inside the frame where possible but where the car is back halfed I ran -8an to the fuel pump. I also ran -8an from the 1/2" hard line to the firewall mounted reg. I will build a plate later to move the reg. to in front of the carb but for now it works.
 
#15 ·
Billy, I tried to snake my fuel lines up in the rails....that part of the frame that arches over the axel, and I coulnt get it to go up in there, there was something blocking it. I tried my electrical fish tape, and couldnt get it in there.
 
#22 ·
Was it a hard line that you were trying to do that with, or steel braided hose? This is why I'm leaning towards the braided hose, because I don't think that I'll ever be able to snake hard line through the entire frame rail since I have it all boxed in, and I'll have to slide it in beginning from BEHIND the rear wheels.

It has to be shielded in the flywheel area. Don't be sliding down no guard rails, mine was inside the frame and it cut the frame and the fuel line ;)
Gee Bob, I didn't realize that you had frame damage too during that mishap.

Hey....where's Billy....I PM'd him with my email...no pics??? :noway:
I didn't forget you. I was in work. I'm a mechanic, so I can't be hangin around the computer at work. I'll start sending you some pics now.;)

Well bill I was gonna go and take pics but its too darn cold lol. sorry Ill prolly get them taken after you don't need them anymore lol.
Well whenever. It will likely be sometime in late February I'll begin the fuel system install.
 
#16 ·
I've got my braided line going the entire length of my frame rail, on the inside. For the most part you can see it just fine, there are a few areas where the frame is boxed from the factory that you can't see the line 100%, but I don't really think it's all that big of a deal. It's tied back with rubber insilated clamps every 12" or so, which are bolted to the frame. The hose is -8 AN, and is holding it's shape, so it's pretty obvious by looking at what you can see what the rest of the line is like.
 
#21 ·
Well bill I was gonna go and take pics but its too darn cold lol. sorry Ill prolly get them taken after you don't need them anymore lol.
 
#27 ·
If you are going steel braid, be careful they don't like unleaded fuel. It may be pain in the butt to change out the line in a few years. I had #10 line run through the frame with the stock frame, and it is inside the 2X3 Frame rail now after the backhalf.
 
#29 ·
If you are going steel braid, be careful they don't like unleaded fuel. It may be pain in the butt to change out the line in a few years. I had #10 line run through the frame with the stock frame, and it is inside the 2X3 Frame rail now after the backhalf.
I've heard that before Ray. Thanks for the heads up. The thing is, I don't know if I can use hard line, since the body is already on the frame, and I'll be using a considerably bigger diameter than the factory did. And since I've boxed-in the frame rails, I think that if I'm going to place the line inside of the rail, then I'll have to start it inside the rail from BEHIND the rear wheel.

I'll have to crawl under there and take another look to be certain about that, but if I'm correct on that, then that means that whatever fuel line I DO use, will have to be snaked up, over, and through the frame rail arch which goes over the axle tube. But I'm very skeptical about being able to get a 5/8" diameter hardline through that arch successfully without kinking it. So I might not have a choice but to use steel braided hose since it's more flexible than hard line is, and therefore should go easier through that arch way of the frame rail near the rear tire than hard line would.
 
#28 ·
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#30 ·
I'd highly recommend the teflon lined braided, especially if you're putting in boxed rails. I went through a major hassle about a year ago trying to find where my rubber lined braided line was weeping. Looked fine from the outside but it was a bit squishy where the lining had broken down. No more gas fumes in the garage now.
 
#31 ·
OK, but for me, I might be commited to Russel braided hose, since I've already spent a lot of $$ on a number of their hose ends, and from what I'm hearing, you cannot use one manufacture's hose ends with another one's braided hose since the OD's of the hose are different from one manufacture to the next, and they make their hose ends accordingly to fit their own braided hose.

For instance, I've noticed that Russel's -10AN size steel braided hose has a different O.D. than the -10AN braided hose from some other manufactures. And I'm bringing that up because I've noticed that many manufacture's of braided hose (including Russell) only offer the teflon lined hose in smaller sizes for brake lines (ie. -3AN, and -4AN only).

Another thing that would concern me would be that I've heard that the teflon lined hose is not as flexible as other braided hose is. So I wonder if I'd be able to snake it through the wheel arch of the frame rail. But the numerous Russel hose ends and fittings I've already purchased might pretty much have set my course for this part of my project.
 
#32 ·
You're probably right about the fittings. The stuff I got has fittings that needed to be crimped onto the ends (with a special machine), but I think some brands use screw-on fittings. It also has a much smaller OD than comparable ID rubber stuff. They aren't as flexible, but should be flexible enough for going around the frame rail.

Aeroquip makes it in any size you might want -http://www.aeroquip.cc/aeroquipracehose.aspx. I have the Dupont version (called Teleflex).

If you go with the rubber line, I'd be prepared to replace it every few years unless you never let gas sit in the lines for too long. I strongly recommend trying to sell/return what you have (especially if it's not used) and go teflon-lined.
 
#33 ·
Mark, thanks for the link. I just used it to go on their website, and the funny thing is although many guys often recommend the teflon lined hose like you have, the Aeroquip webpage lists these uses for that hose:

"Brake fluid, transmission, power steering, air conditioning, and hydraulic" but that's it. they do not list that hose for being intended for gasoline. Their other hose called their "AQP" hose lists fuel for being one of the intended uses, and that hose HAS A RUBBER LINING.

So I wrote to them and asked if their teflon hose is intended for fuel, and if it is then why doesn't it say so on their website. And BTW, yes, Russell hose ends can be installed onto their braided hose without the need for any machine. Only a vice is required.
 
#34 ·
Bill, I'm running -8 pushlock (X2), which has a large OD, like 3/4". The braided -8 is much thinner. Still, I just couldnt even get a fish tape through those rails. Who knows, my car could of been hit or something and kinked the frame, causing a blockage.
 
#36 ·
Hmmm, thanks for the heads up on that Vince. I guess I'll find out when I try it out on my car.

The stuff I got is advertised for fuel. I got it at the local Amazon Hose and can't find anything but the Dupont write-up for it on the web (http://www2.dupont.com/Automotive/en_US/applications/caseStudies/case018.html)

I'm pretty sure the Aeroquip stuff is good for fuel. It would be cool if you could let us know what they tell you.
OK yes, I'll let you know what their answer is. Some of these aftermarket companies DO have wrong information about their products on their own websites, so we will see what answer they give me.
 
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