Mercedes Mullins
LS engine swaps are a popular upgrade among car enthusiasts, as they offer a significant boost in performance. One of the most important parts of this upgrade is ensuring your new LS engine receives the right amount of fuel. Fuel lines are a key component in any fuel injection system, transporting gas from the tank to the engine. This is facilitated by a fuel pump, which pressurizes the fuel from the tank, allowing it to travel through the fuel lines and into the engine. There are two fuel pump types for LS engine swaps: in-tank and external. This article will provide a step-by-step guide on how to build fuel lines for an LS swap, covering everything from selecting the right pump to choosing the appropriate fuel line kit.
LS Swap Fuel Line Characteristics and Values Table
| Characteristics | Values |
|---|---|
| Fuel line kit | AN6 |
| Hose | PTFE-lined, Russell Pro-Classic, rubber |
| Fittings | 6AN, 3/8-inch quick-connect, 5/16-inch quick-connect |
| Pump | Walbro 255L inline, in-tank |
| Filter | 100 Micron pre-pump, 10 or 30 Micron post-pump |
| Regulator | Corvette-style, 58 PSI |
| Return style setup | Requires feed and return line to and from the engine bay |
| Return-less setup | Does not require a return line |
| Evap lines | Not necessary to remove |
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What You'll Learn
Differences between in-tank and external fuel pumps
When it comes to building fuel lines for an LS swap, one of the key considerations is the choice between an in-tank and an external fuel pump. Here are the key differences between the two options:
In-tank fuel pumps are immersed in fuel, which has several advantages. Firstly, the fuel helps to cool and lubricate the pump, prolonging its lifespan. Additionally, being surrounded by fuel and enclosed within the tank, in-tank pumps operate more quietly than external pumps, which can be important for vehicles that see a lot of street use. In-tank pumps are also self-contained units, simplifying fuel system plumbing and mounting. They are also protected from physical damage, which can be a concern with external pumps that are exposed to the elements and potential road hazards.
On the other hand, external fuel pumps are typically easier to install, as they don't require modifications to the fuel tank. They are also more accessible for maintenance and repairs. External pumps can be noisy, producing a whirring hum that may be undesirable, especially in classic or luxury vehicles known for their quiet and smooth operation.
In terms of performance, in-tank pumps create positive pressure in the fuel lines, aiding in pushing gasoline to the engine. They are also less likely to run dry and burn out compared to external pumps.
For LS swaps, popular choices for in-tank pumps include the Walbro 255L inline pump and the Holley Sniper EFI fuel pump module kit, which offers adjustability for different engine configurations. For external pumps, the Sniper EFI kit from Holley is also recommended, as it comes with a tank and pump, as well as nylon braided hoses and AN fittings.
Ultimately, the decision between an in-tank and external fuel pump depends on factors such as the vehicle's intended use, the complexity of the fuel system, and the desired level of performance and noise reduction.
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Return-style vs return-less setups
When it comes to building fuel lines for an LS swap, there are two main types of setups to consider: return-style and return-less. Here's a detailed overview of each type:
Return-Style Setups:
Return-style setups, also known as return-type systems, are identified by the presence of an integrated fuel pressure regulator on the LS engine's fuel rail. This type of setup utilizes both a feed line and a return line to and from the engine bay. The fuel pressure regulator in this configuration is built into the fuel rails themselves. As a result, more hose is required compared to return-less setups. The main fuel filter is typically positioned on the feed line, ensuring that fuel is filtered before it reaches the engine.
One advantage of return-style setups is that they offer more precise fuel pressure control, making them well-suited for highly tuned or performance-focused engine setups. Additionally, the return line helps to purge any air bubbles from the fuel rail, preventing misfiring and keeping the rail and injectors cool by circulating fuel. Return-style setups also provide flexibility in terms of regulator location, which can be placed near the fuel tank for a shorter return line.
Return-Less Setups:
Return-less setups, on the other hand, feature a streamlined design where fuel is sent from the tank to the engine via a single feed line, with no return line. This ensures that only the fuel needed by the engine is delivered. Return-less setups typically do not have a built-in pressure regulator but instead use alternative methods, such as an external fuel pressure regulator or pulse width modulation (PWM). While PWM is prevalent in modern OEM setups, it is less common in the aftermarket.
Return-less setups, such as the Corvette-style filter and regulator unit, offer a simplified solution for LS engine swaps. They combine fuel filtration and pressure regulation in one package, making them ideal for street rods, street/strip cars, trucks, and custom builds. When used with compatible fittings, these setups can further ease the plumbing process of the fuel system.
In summary, the choice between a return-style and a return-less setup depends on the specific needs and preferences of the LS swap project. Return-style setups offer more precise fuel pressure control and the ability to purge air bubbles, while return-less setups provide a streamlined design and simplified fuel system installation.
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Fuel line routing and cooling
First, it is important to determine whether your engine is a return-less setup or a return-style setup. This will impact the routing and cooling configuration. Return-style setups have a fuel pressure regulator integrated into the fuel rails, requiring both a feed line and a return line to and from the engine bay. In contrast, return-less setups do not have this regulator and only require a single feed line.
For return-style setups, the fuel pressure regulator is often placed near the fuel tank to allow for a shorter return line. This setup can help maintain cooler fuel temperatures, as the return line provides circulation and cooling to the fuel rail and injectors. Additionally, a return line can improve performance by purging any air bubbles from the fuel rail, preventing potential misfiring issues.
When it comes to fuel line routing, there are a few options. One common method is to use an AN6 fuel line kit, which provides an effective setup with minimal effort. This kit allows for easy installation from the tank to the regulator to the fuel rails. Another option is to adapt existing metal lines with fuel injection hose and clamps, especially where the metal line breaks between the subframe and the rear frame. It is recommended to use PTFE-lined hose or Russell Pro-Classic hose and fittings for flexible connections to avoid fuel-related damage to rubber hoses.
Finally, consider the fuel pump type—in-tank or external. In-tank pumps offer benefits such as increased durability, better handling of high pressure, reduced noise, more efficient fuel delivery, and lower chances of vapor lock. However, they are more complex to install and retrofit. For LS engines, the pump must deliver 58-60 psi of pressure to the injectors, with a flow rate of 240-340LPH, depending on horsepower.
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Using the correct fittings
For a return-style setup, you will need to select a fuel pump that can deliver the necessary pressure and flow for LS engines, typically 58-60 psi with a flow rate of 240-340LPH. The stock fuel rail setup for this configuration typically uses 3/8-inch quick-connect fittings on the feed line and 5/16-inch quick-connect fittings on the return line. It is important to ensure that your fittings match these specifications.
If you are working with a return-less setup, you may need to adapt your current metal line. This can be done by swapping the hose where the metal line breaks between the subframe and the rear frame with fuel injection hose and clamps. It is recommended to use PTFE-lined hose or heat wrap/heat sleeve near heat sources to protect against fuel harshness and fumes.
Additionally, for both setups, you may need to install bulkhead fittings into the tank to ensure a constant feed of fuel to the pump. For LS swaps, a Walbro 255L inline pump is a common choice, which can be converted to AN6 style fittings. Pre-pump, a 100-micron fuel filter is recommended to protect the pump from debris, and post-pump, a minimum of a 30-micron filter or a recommended 10-micron filter should be installed.
Finally, a regulator is required to deliver the necessary PSI to the LS fuel rails, typically around 58 PSI. A Corvette-style regulator and combination unit is a popular choice for LS swaps.
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Fuel pressure and flow
Firstly, determine whether you have a return-style or return-less setup. This will impact your fuel line installation process. Return-style setups are commonly found in ''04 and earlier truck-based LS engines, while newer engines may have a return-less configuration. Return-style setups require both a feed line and a return line to and from the engine bay, whereas return-less setups are relatively straightforward and typically use AN hose and fittings.
When selecting a fuel pump, ensure it meets the flow rate and pressure requirements of your LS engine. In-tank pumps are generally preferred as they tend to last longer, hold higher pressure, and operate more quietly. For return-style setups, consider using a Walbro 255L inline pump, which can be easily converted to AN6 style fittings. It is also crucial to install a fuel filter pre-pump to protect the pump from debris. A minimum of a 30-micron filter is recommended, but a 10-micron filter will provide better protection.
The fuel pressure regulator plays a vital role in maintaining the required fuel pressure. In return-style setups, the regulator is often placed near the fuel tank to allow for a shorter return line. The Corvette-style regulator is a popular choice for LS swaps, providing a fixed fuel pressure of 58 PSI. However, some swappers prefer a dual-line system to maintain cooler fuel temperatures, while others opt for a single-line setup. It is important to note that fuel pressure can vary based on load, and the regulator adjusts pressure accordingly to prevent the engine from running lean.
Additionally, consider using PTFE-lined hoses or Russell Pro-Classic hoses for any flexible connections to avoid fuel-related damage to rubber hoses. Proper fittings, such as the AN6 fuel line kit, can also ensure an effective setup with minimal effort.
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Frequently asked questions
There are two types of fuel pumps for LS engine swaps: in-tank and external (inline). In-tank pumps are more durable, handle high pressure better, produce less noise, deliver fuel more efficiently, and have a lower propensity for vapor lock. External pumps are easier to install, cheaper, and offer easier maintenance and replacement.
For LS engines, you need a pump that can deliver 58-60 psi of pressure to the injectors, with a flow rate between 240-340LPH.
In a return-style setup, the fuel pressure regulator is integrated into the LS fuel rails, requiring both a feed line and a return line to and from the engine bay. A return-less setup is commonly used in LS swaps and provides a simple solution for fuel delivery to the engine.
You can use an AN6 fuel line kit for LS swaps. You can also use an LS-LINE-KIT or LS-LINE-KIT45, depending on your tank type.
It is recommended to install a 100 Micron Fuel filter pre-pump to protect the pump from debris. Post-pump, a 10-micron filter is recommended, although a 30-micron filter is the minimum. A Corvette-style regulator is a common option for LS swaps.
