Believe it or not, there's a lot to know about upgrading fuel lines. The process isn't as simple as grabbing whatever's on the shelf and tossing it in your car. In the best-case scenario, that leads to possible leaks. Worst-case scenario? You burn your car to the ground.
Whether you want to update an old, tired setup that doesn't really work in today's day and age, or you’re just looking to increase the volume of fuel that's supplied to the engine, upgrading fuel lines can improve your car’s performance and enhance its efficiency.
It’s easy to get overwhelmed by the varying information that's put forth by manufacturers in this space. The good news is that while everyone in the industry has their own way of doing things – and you will have to find whose product is best for your needs – we can give you a basic rundown that'll help you make an educated decision.
Safety First
We're dealing with internal combustion engines here. More specifically, we’re dealing with the part that really aids with combustion. As mentioned in the intro, changing around fuel lines isn't something to take lightly. The safety risks involved can turn a single wrong move deadly.
Always make sure you're using a fuel line that's compatible with your fuel, and route it to minimize as many risks as possible.
Common sense will take you a long way, but falling back on DOT regulations and rulebooks put forth by sanctioning bodies will certainly help clear up any questions you may have. In most cases, they will spell out what's acceptable in plain English, making the hardest part for you ponying up for the necessary parts.
That said, rules are good motivation for upgrading fuel lines in the first place as many race tracks don't accept what's allowed on the roads. So, if your goal is to improve the safety of a street vehicle, then referencing these rules can be very helpful. Bits of information – such as the NHRA allowing no more than 12 inches of rubber hose in the entire system – give you an idea of how to make your car safer on the road.
Carbs vs EFI
Safety extends to pressure considerations, too. That’s why, when you swap from carbs to EFI, upgrading fuel lines is crucial. Carburetors operate at a much lower pressure, and failing to upgrade can result in catastrophic ruptures due to the increased pressure from EFI.
This is very important information because while carburetors may no longer be on production vehicles, they are ever-prevalent in the world of performance. That means, many manufacturers are still producing carburetor-specific fuel lines.
You must be careful and make sure any fuel lines you select are rated to handle the pressure your fuel system is running at. For the record, carburetors can run with high-pressure lines, but this generally will drive up the cost for no real reason.
Fuel Line Materials
Modern fuels are highly corrosive. Over time, they will break down your vehicle’s fuel lines, creating leaks and clogging up the system. Manufacturers use a variety of different materials with varying levels of corrosion and abrasion resistance to help combat this issue. To ensure you choose the right fit for your application, read the product literature closely so you understand the benefits each style (and manufacturer) brings to the table.
For a head start, here’s a basic rundown of the most common materials.
Metal Hard Line. Rigid metal lines are commonly used on OE-type fuel lines, specifically in areas where the fuel lines are exposed to road conditions, such as beneath the vehicle. This material offers maximum protection but is difficult to bend, making routing a challenge even with the right tools. Thankfully, pre-bent lines are available for many applications to ease installation.
Rubber is the most common and affordable option. It's also very easy to work with and can be compatible with both high and low-pressure systems. You can often run down to any parts store and grab it off the shelf in custom lengths, further adding to desirability. Unfortunately, rubber hoses break down quickly and need to be replaced frequently on account of leaks. They're a safety concern for track use, so minimizing their presence – if not eliminating them entirely from your fuel system – is often required.
Nylon is similar to rubber in that it's easy to route and readily available. It is, however, more costly and difficult to insert fittings into on account of its stiffer nature. The benefit of nylon is that it offers much better corrosion resistance and generally serves as a step-up for people who want something longer lasting than rubber but don't want to invest in costly race-rated lines.
Polytetrafluoroethylene, or Teflon, is basically what you want for anything performance-related. This material offers excellent corrosion resistance and is safe to use with race fuels. It also offers much lower surface friction than other materials, giving it an advantage in terms of flow as well. The tradeoff is that it's far more costly than your alternatives.
Is Braided Better?
Aftermarket fuel lines are often covered with a braided barrier to provide extra abrasion resistance. Despite the marketing copy devoted to this feature, it shouldn’t be prioritized over the materials the fuel will actually be in contact with. (It doesn't matter how good a line looks if the materials inside will break down rapidly.)
Braided barriers can be life savers in the right applications, as they do add an additional layer of protection against abrasion and external damage. The construction also helps prevent kinking. However, the choice between braided and non-braided fuel lines depends on the specific needs of your vehicle and its intended use. Exterior aesthetics should always be a secondary concern. Far too many subpar brands on dropship sites prey on folks who want looks over performance, and the results can be deadly.
Picking the Right Diameter
As performance increases, the demand for fuel rises with it. Along with moving to a higher volume pump, larger diameter fuel lines will gradually need to be added. Exactly what diameter you should consider is dependent on factors specific to your vehicle, such as the horsepower level, pump specs, and pressure requirements.
It's important to note that, when upgrading fuel lines, bigger is not always better. While most performance applications can benefit from a slight bump over stock, you can go too far. Too big of a line will directly impact the ability for pressure to build within. Do your research and consult with professionals to determine what's best for your particular build.
Most aftermarket fuel lines use AN fittings and sizes. AN just means Army Navy and is simply a unit of measurement that was standardized back in WWII. These sizes refer to the OD of the tubing in 1/8-inch increments, starting at AN -2 (measuring 1/8-inch) up to AN -32 (measuring 2 inches).
Keep in mind that the fittings matching this style have a standardized thread pitch. Switching to these fittings means upgrading the entire fuel system to match. Often times, moving to an aftermarket fuel pump drives this change as they are usually designed to use AN fittings.
Installation Tips
You probably guessed that installation varies case by case. The practices you need to implement on one application can be vastly different from another. Therefore, there is no universal step-by-step guide. However, here are a few general tips that will help you avoid major headaches.
Stick to One Brand. Manufacturers often design their fuel lines to work exclusively with their fittings, ensuring compatibility. Mixing and matching can lead to leaks, pressure variances, variations in thread pitches, and other problems. Pick one brand and use the fittings it recommends for the specific fuel lines you're using.
Use the Right Tools. Whether you're bending tubing or crimping fittings in place, you need to use the right tools to avoid kinks, poor seals, and other problems. If you’re unsure or prefer not to invest in the proper tools, then consider having a professional build your fuel lines for you.
Thoughtful Routing. Be mindful of where you route your fuel lines. You must avoid any areas that put the lines at risk of punctures, dings, dents, and sources of heat. All of these issues are major safety concerns and can absolutely destroy performance.