HOW TO MAKE YOUR CUSTOM CAR NEXT LEVEL
Have you watched MOOG's latest video on his XR8 Falcon engine swap? It's RIGHT HERE for your eyeballs' pleasure in case you haven't, BTW, but in that video MOOG gets on with making fuel lines with AN fittings.
Now, maybe you've never played with fuel systems before so before you go reading on below it might pay to read THIS STORY on AN fuel fittings and lines to work out what is going on. This is because we're going to dive into the next phase of custom car plumbing: hardlines.
If you hang around high-end car shows or motorsport events you can see some details on cars that you really don't see anywhere else, and one of these details is beautifully arranged hard line installs. Hard lines can be any sort of metal tube, but normally they're made of steel or aluminium, as opposed to rubber or braided flex lines you may be used to seeing in custom installs.
While I was making a new AN10 fuel line for the back of my Harrop-supercharged '64 Pontiac [CLICK HERE FOR THE VIDEO ON IT] it is a pretty simple piece. To demonstrate how cool hard line can look I've pinched some photos from Phil at Pro Gen Performance and Auto Hoses, because he is an absolute wizard with making beautiful-looking, well laid-out, and engineer-approved hard line installations.
If you want to know more about how to make your own braided or rubber fluid lines, you should start with THIS STORY HERE that I did a while ago about AN fittings.
This is important to understand because you'll likely have to use some AN fittings to join the hardline to whatever part you're connecting, or as a flexible link between fuel components mounted to the body or engine, and hard lines mounted firmly to the chassis.
Having flexible hose between components mounted to the body, and parts mounted to the engine, will provide important vibration damping. This will prevent breakages and premature wear, which is especially important for fuel lines - you don't want to be stuck by the side of the road with all your fuel gushing onto the ground (I have recently had this issue when a part failed).
Using custom-bent metal pipes in place of traditional rubber or braided lines is more time-consuming to do, more difficult to plan and execute, and requires a few specialty tools. However, many engineering signatories would prefer you use a majority of hard line rather than rubber or braid for fuel lines.
Hard line installs can also be much more compact thanks to their rigid nature and ability to handle tight bends better than hose, and while hard lines can crack or fatigue through age or improper support, they won't collapse or degrade internally like rubber line. They also look fantastic when installations are carefully planned out.
Choosing the right material to use is the first step. Aluminium is lighter and easier to bend, but not as strong as steel line. Aluminium's heat-shedding abilities does make it attractive for those making custom heater or water:air intercooler lines, but it is not suitable to be used for 45-degree flares, brake lines, or high-pressure lines, like what is needed for power steering, air suspension, or some other high-pressure oil lines.
If you're not sure what material you should be using for the different parts of the car, do some research into what pressure the various parts of the car will see. You can then check with hydraulic component suppliers (like Pirtek or ENZED, for 2 examples) as to what they'd make the lines out of.
Joining your hard line to the parts and hoses will normally be done with aluminium AN fittings, as described above. When using aluminium tube for fuel or oil lines you can use tube nuts, which seat on a 37-degree flare as per regular AN fittings, and don't require welding on like steel fittings.
One tip I like to use is to put a tag of brightly coloured tape around BOTH ends of the tube after I cut it just to remind me to check if I need to weld the fitting on, or add the tube nut, BEFORE I get distracted, flare the pipe, and then realise I wasted all that time and pipe.
In the pic below I have mapped out how I'd like the fuel feed (left-hand side) and the fuel return (right-side) would run and be affixed to the chassis BEFORE I committed to flaring the ends or adding fasteners. It took me quite a while to roll the line out straight, then add bends in the right spots, and work out where I should add joiners should I ever need to service the fuel system.
Designing your installation can take a little time to find the best way to run the tube, and find all the spots to support it properly. Use proper-fitting P-clips fastened to the chassis or body to support the line, and the number of these will depend on the type of metal you're using and diamtre of the pipe.
You should also work out how easy the lines will be to remove from the car in case you need to repair or service them. Adding some bulkhead joins to aid fitting or removal can mean the difference between a speedy road-side repair, and stripping your car to correct a simple problem.
Metal hard line is sold in per-metre (or feet in countries using Ye Olde Measurements) lengths, normally rolled into a coil. This means you'll need to straighten the tube before you try installing the bends you need, but don't race in and start hand-pressing it as you can easily kink small-diametre tube, and large diametres will just make your hands hurt.
There are tube-straighteners you can buy which make the job far simpler. You basically just pass the tube through the rollers backwards and forwards to get your lenghts ready for bending.
You can use a grinder or hacksaw to cut the tube, but there are also special pipe cutters available incredibly cheaply which will ensure a dead-straight cut across the face of the tube every time. This is vital for getting a good seat on the fitting, which in itself is paramount if you don't want fuel, oil, transmission fluid, or coolant hosing out under pressure (and then catching fire).
Once the tube is cut the end needs to be dressed with a deburring tool to remove sharp edges and swarf. These are normally sold with the tube-cutter.
Bending the tube isn't terribly difficult but it does take practice to get neat. Just like welding or spray painting, this is a skill you'll build rather than being an absolute guru from the first time you try it, so consider having a few practices on scrap tube before you try to make the lines for real.
Start with simple bends and shapes on small-diametre tube first, as this will teach you how the metal moves - you can overwork it, stretching it too tightly and making it thin, or causing it to kink in other parts so have a practice before commiting. Planning out a section with a few simple bends to start is a good idea, and then work from there into more complex shapes, layouts, and compound bends.
Once you're happy with your line, fit it up with some fresh P-clips and revel in the new skill you've discovered.
