Sylvie Willis
When upgrading a carburettor to an electronic fuel injection (EFI) system, it is possible to use the factory hard metal line as the return line. The size of the fuel line will depend on the engine. For most V-6, I-6, and V-8 engines, a 3/8-inch fuel line is appropriate, while a 5/16-inch line will suffice for smaller V-6s and I-6s. For a high-horsepower V-8, a 5/8 line and hose may be required. For a four-cylinder engine, a 5/16-inch hose and metal line are usually sufficient, although a 1/4-inch line may be used for low-powered four-cyl engines. Some people prefer to use hard lines along the frame, while others opt for braided steel lines.
| Characteristics | Values |
|---|---|
| Hose size | 3/8-inch fuel line is appropriate for most V-6, I-6, and V-8 engines |
| Hose size | 5/16-inch will suffice for the smaller V-6s and I-6s |
| Hose size | 5/8 line and hose for a high-horsepower V-8 |
| Hose size | 5/16-inch hose and metal lines for four-cylinder engines |
| Hose size | 1/4-inch for low-powered four-cyl engines |
| Hose size | -6 is the smallest size recommended |
| Hose size | -4 is rated to 1/4-inch ID hoses |
| Hose size | 1/4-inch ID hoses would restrict the system on a 5/16 fuel system |
| Hose type | Braided steel |
| Hose type | Flexible |
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What You'll Learn
Braided steel lines
When choosing braided steel lines for fuel injection, it is important to consider the size of the lines. The size of the lines will depend on the engine size and the fuel system's pressure requirements. For most V-6, I-6, and V-8 engines, a 3/8-inch fuel line is appropriate. For smaller V-6 and I-6 engines, a 5/16-inch line may be sufficient. For a high-horsepower V-8 engine, a 5/8-inch line may be needed.
It is also important to use the correct fittings and clamps with braided steel lines to prevent leaks. Fuel injection hose clamps are available from suppliers such as Ideal, and can be purchased online. Braided steel lines can also be used with rubber hoses, which can be sourced from suppliers such as Rock Auto.
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Factory hard metal lines
If your vehicle had a carburetor and you are upgrading to EFI, you can use the factory hard metal line as the return line and build a high-pressure feed line to feed the system. Generally speaking, 3/8-inch fuel line is appropriate for most V-6, I-6, and V-8 engines and sometimes 5/16-inch will suffice for the smaller V-6s and I-6s. You may want to go to 5/8 line and hose for a high-horsepower V-8. For a four-cylinder, you can get away with 5/16-inch hose and metal lines, and sometimes 1/4-inch for low-powered four-cyl engines.
If you are building a custom fuel system, you may want to consider using hard lines along the frame. You can bend these yourself or buy mandrel bent lines.
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Flexible hose systems
When it comes to fuel injection, there are a few options for the hard line. One option is to use a factory hard metal line as the return line and build a high-pressure feed line to feed the system. This is a common approach when upgrading from a carburetor to EFI. The size of the fuel line will depend on the engine, with 3/8-inch fuel lines being appropriate for most V-6, I-6, and V-8 engines, and 5/16-inch lines being sufficient for smaller V-6s and I-6s. For a high-horsepower V-8, a 5/8 line and hose may be necessary.
Another option is to use flexible hose systems. In the past, fuel systems for fuel injection have been built using one of three flexible hose systems. It's important to note that going smaller than -6 can restrict the system, even when using 5/16 flexible line. When it comes to clamps, fuel injection hose clamps from Ideal are an option, and they are cheap and can be mail-ordered.
Some people prefer to use hard lines along the frame, as they can be bent to fit the specific application. However, it's also possible to use a combination of hard lines and flexible hoses, with short pieces of EFI flex hose and EFI hose clamps. It's important to consider whether the hard line will need to be flared to prevent leaks when using flex lines.
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Mandrel bent lines
If your vehicle previously had a carburetor and you are upgrading to EFI, you can use the factory hard metal line as the return line. You can then build a high-pressure feed line to feed the system. The size of the line you need will depend on the engine. For most V-6, I-6, and V-8 engines, a 3/8-inch fuel line is appropriate. For smaller V-6s and I-6s, a 5/16-inch line may suffice. For a high-horsepower V-8, you may need to go up to a 5/8 line. For a four-cylinder engine, a 5/16-inch hose and metal line are usually sufficient, and for low-powered four-cyl engines, you may be able to get away with a 1/4-inch line.
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Fuel injection clamps
When it comes to fuel injection, there are a few options for the hard line. If your vehicle previously had a carburetor, you can use the factory hard metal line as the return line and build a high-pressure feed line to feed the system. The size of the fuel line will depend on the engine, with 3/8-inch fuel lines being appropriate for most V-6, I-6, and V-8 engines, and 5/16-inch lines being sufficient for smaller V-6s and I-6s. For a high-horsepower V-8, you may need to go up to a 5/8 line, and for a four-cylinder engine, a 5/16-inch hose and metal line should suffice, with 1/4-inch lines being an option for low-powered four-cyl engines.
Another option is to use braided steel lines, which can be more flexible and easier to work with than hard lines. Braided steel lines are also available with 90* Russell fittings, which can be useful for certain applications.
When it comes to fuel injection clamps, there are a few options available. Fuel injection hose clamps from Ideal are one option, and they are relatively inexpensive and can be mail-ordered. EFI hose clamps are another option, and they are designed specifically for EFI systems. It's important to ensure that the clamps are properly sized for the fuel lines and that they are installed correctly to prevent leaks.
In addition to the type of line and clamps, it's also important to consider the fuel injection system as a whole. The fuel pressure, flow rate, and other components such as the fuel pump and injectors will all play a role in the performance of the system. It's always a good idea to consult with a professional or a mechanic if you're unsure about any aspect of your fuel injection system.
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Frequently asked questions
Braided steel hard lines are often used with fuel injection. You can also use a factory hard metal line as the return line and build a high-pressure feed line to feed the system.
The size of the hard line you use will depend on the engine. For most V-6, I-6, and V-8 engines, a 3/8-inch fuel line is appropriate. For smaller V-6s and I-6s, a 5/16-inch line may suffice. For a high-horsepower V-8, you may need to go up to a 5/8 line. For a four-cylinder engine, a 5/16-inch hose and metal line are usually sufficient, and for low-powered four-cyl engines, you may be able to use a 1/4-inch line.
Yes, you can use a flexible line with fuel injection. However, you should not go smaller than a -6 size, even if you are using a 5/16 flexible line, as this would restrict the system.
It is not clear whether flaring the hard line is necessary to prevent leaks. Some sources suggest that you can hook a hard line straight to a flex line without flaring it, while others recommend using EFI hose clamps to prevent leaks.
