How To Install LS1 Fuel Rails

Upgrading the fuel system in your LS1 swap can be difficult for those not familiar with working on V8 engines. Because of the dual fuel rails and the returnless system, it’s important to plan out your modifications ahead of time. Not planning your fuel mods could cause you to discard parts or re-do work that’s already been done.

The stock LS1 fuel pressure at the rail should measure 57 psi to ensure proper operation on an untuned ECU. To achieve this target pressure in our LS1 swap, we’ll be installing the complete CX Racing LS1 Fuel Rail Kit part number CXR-FUELRAIL-LS1-Kit-AN8-4P.

We’ll also be installing a set of 31lb injectors (310cc injectors) as an upgrade for our LS1. For our How To Install LS1 Fuel Injector Article, check this link here. We’ll be showing you how to install this unit in a 1993 Nissan 240SX S13 with a LS1 swap, and the Hinson Supercar LS1 Mount kit.

This vehicle is equipped with a Walbro 255 non high pressure fuel pump, which flows over 255lph @ 14 volts. Without a fuel pressure regulator to crank down the pressure, the fuel pressure will be much too high for the motor to run properly. Instead of tuning the vehicle, we’ll be installing this fuel rail kit to get us to our target psi.

A copy of the popular Aeromotive LS1 fuel rail kit, this CX Racing LS1 Fuel rail Kit comes with everything you need to mount your fuel injectors and the fuel pressure regulator. Because this is being installed in a S13 and because of how close the fuel tank assembly inlet and outlet ports are, we’ve decided to terminate the stock fuel lines at the firewall with -6 AN fittings.

Using Red Horse Fitting part number 3100-06-06-1, we’ll be terminating the stock fuel lines to accept a -6 AN.

Take a look at the fitting to familiarize yourself with how it works. The center brass compression fitting will be responsible for sealing the factory fuel line against the Red Horse fuel fitting.

Unscrew this fitting to get to the brass compression fitting inside the two pieces.

Take this fitting out and use a pipe cutter to cut the fuel lines that run along the firewall on your Nissan 240SX S13. Open your gas cap to release the pressure in your fuel system, and undo the feed and return lines that go to your fuel filter and from your fuel rail to the tank.

Once these lines have stopped leaking, you can clean up the area and get ready to cut the factory fuel line itself. Make sure to cut as straight as possible so that your Red Horse compression fitting can easily slide over and compress.

Terminate both the feed and return fuel lines so that your vehicle can now accept the -6 AN female swivel fittings. Make sure you tighten the compression fitting enough so that the brass ring crushes and seals your factory fuel lines. This is the one location where you MUST take the proper precautions upon startup to ensure there are ZERO LEAKS.

Now with your car’s fuel lines terminated properly, let’s remove the stock fuel rail and injectors and install the new units.

As with all of our writeups, if you do not feel comfortable working on your vehicle, stop. Take your vehicle to an experienced mechanic that knows what they are doing with your LS1 swap.

Your fuel system and rail should be bled of fuel and pressure, so go ahead and undo the injector clips.

Next unplug your MAF and TPS in order for the entire wiring loom to move. You will be removing the 4 bolts that hold the fuel rail on to your LS1 intake manifold.

Remove all four of the 8mm bolts that hold the LS1 rail onto the intake manifold.

Once you have the right side of the fuel rail loose, go ahead and unclip the factory fuel feed fitting. Because this LS1 fuel system is returnless, all you have to do is undo the rest of the bolts for the fuel rail to lift off the manifold.

Once you’ve got all the bolts taken out you can now carefully lift on the front and the back of the rail at the same time, lifting off your injectors and rails.

 

To make this CXRacing fuel rail fit, you will need to remove the bracket located on the driver side of your LS1. This bracket must be removed for both rails to fit and clear your LS1 or LS6 intake manifold.

Remove these bolts to take off the bracket, giving you enough clearance along the intake manifold to begin mounting your rails.

Take a break here in our How To Install LS1 Fuel Rails article and clear your intake manifold of any debris. Take the proper precautions so that nothing can fall into your motor or intake by way of the injector holes. With your stock fuel system removed, you can now move onto the CX Racing LS1 Fuel rail kit.

Take the blue -6 AN male fittings and isolate them with the rubber o-rings provided to you in the kit. Screw these fittings into either end of your fuel rails and tighten down.

Next turn your attention to your CX racing fuel pressure regulator, and the liquid filled fuel pressure gauge that came with the kit.

You can opt to install the manual liquid filled gauge, or install a remote sender if you’ve got a electronic fuel pressure gauge inside your cabin.

Remove the 8th inch NPT plug from the front of the fuel pressure regulator, and teflon tape the fuel pressure gauge before installing. You can take a couple of different routes here when it comes to the install of your aftermarket LS1 fuel rail, by either mounting the FPR directly onto the rail or on the firewall.

Keep in mind however if you are not mounting directly to the fuel rail itself, you will need more fittings to terminate the fuel system at the regulator. You will need a total of six new hose ends if you are going to mount the regulator away from the fuel rail. These RedHorse skus : 1045-06-1 and 1090-06-1 should help you get the job done.

The CX Racing LS1 Fuel Rail kit does not come with a crossover pipe, or the -6 line that connects one rail to the other.

Now turn your attention back to your factory rail and injectors for the next part of our How To Install LS1 Fuel Rails article. Using a flathead screwdriver remove the metal clip that secures your stock LS1 injector in place.

Note the orientation of the CXRacing LS1 Fuel Rail kit with your stock fuel rail to get a clue as to how your rails will be laid out. Unfortunately, because these LS1 Fuel rails are all one rail in reality, you will need to flip flop these rails to get the injectors pointed in the right direction.

Install the new injectors in the CX Racing LS1 Fuel Rail Kit, but make sure to double check your injector o-rings for damage first. Gently lubricate the outer o-ring with a slight dab of vaseline. Do not overuse the product or allow any to touch the injector boss or inlets. Remember that just a little is needed to help guide these injectors in place. Replace any o-rings in the event that you see any tears or rips in the oring itself.

With your new injectors installed in your new fuel rails, you can now move onto our least favorite part of this How To Install LS1 Fuel Rails article. Or at least the least favorite part of the CX Racing LS1 Fuel Rail Kit, because this mounting system is a bit problematic. We’ll be talking about that later in our How To Guide.

Install all four legs through the CX Racing fuel rails but do not tighten the hex nuts. Because this kit does not come with the proper replacement bolts for re-installation, you will need four new 10mm x1.25 bolts that are long enough to reach through the mount to the intake manifold.

Your stock bolts will not fit back through the large CX Racing fuel rail mounts, making this product a bit more problematic than we originally planned. Luckily for us these bolts are plentiful in Hondas and many other import applications, a quick rummage through the shop nets our solution.

You are looking for your injectors to fully seat inside the intake manifold, remember to flip them on the motor because these rails are not really engineered or designed for this motor because they are just one fuel rail.

 

Once your injectors are installed, test mount the CX Racing LS1 Fuel Rail kit to measure the distance between the two rails. Measure this distance and then compile a new crossover pipe.

Click here for our How To on Making Hose Ends for your performance vehicle.

Get that crossover pipe done and you can now bolt in the fuel rail kit.

Connect the feed from the compression fitting you installed earlier, and then connect the return to the bottom of your CX Racing Fuel Pressure Regulator.

 

You will need the bottom of the regulator to head to your fuel return, make sure to terminate your return at the firewall or at the pump correctly. Once you have tightened all fittings and swivel AN hose ends as well as the fuel rails, go ahead and turn the key to the “ON” position.

Check all your compression fittings, all AN fittings, the injector bosses on the intake manifold and all the fittings at the fuel pressure regulator. Adjust the top of your fuel pressure regulator and dial down the fuel pressure to your target 57 psi. With any luck you will not need to retighten or address any leaks or issues.

What we didn’t like

1. Outside of the obvious issues behind the fuel rail design, we didn’t like the 8th inch NPT holes on top of each fuel rail. The rails themselves are not smooth and have ridges, making installation of a plug or a gauge sketchy at best.
2. There is no crossover pipe provided, nor are there any new bolts for the old intake manifold bolts that were removed.

Overall however for under 200 dollars, it’s a hard package to beat for this price break. We would recommend this LS1 fuel rail kit for those enthusiasts that are more comfortable with AN fittings and working on fuel related products.

Congratulations, you have now completed our How To Install LS1 Fuel Rails. Please let us know if you have any questions or comments below!