How To Install A Holley Sniper In-Tank Retrofit Fuel Module

12/06/2022

How To Install A Holley Sniper In-Tank Retrofit Fuel Module

12/06/2022

Installing fuel injection into a classic vehicle is much more common now than it ever has been. Whether that involves swapping in a completely new engine, such as GM’s LS or Ford’s Coyote, or simply adding an aftermarket fuel injection system like Holley’s Sniper to your classic project, fuel injection has become as prevalent as the carburetor.


In the past, making the jump to fuel injection was quite the undertaking. Most gearheads would find a fuel tank from a donor vehicle and make it work as best as they could. There were some aftermarket units, but they weren’t easy to install and required quite a bit of fabrication. Today, however, there are fuel pump options that don’t require the replacement of the original tank.


Rat Rod Fuel Pump T-bucket

This T-bucket project will be running an LS engine for power. Unorthodox, yes. Powerful, yes. But we need a fuel system capable of feeding the modern mill.


For most popular applications companies like Holley make completely bolt-in solutions with brand new tanks designed with high-pressure fuel pumps. But what do you do if you don’t have a popular application? In fact, what if your fuel tank is just a cylinder?


This 1923 Ford T-bucket project is going to be powered by an LS engine…not exactly par for the course with a T-bucket build. However, you can’t argue with the power gains the late-model GM engine provides. With this engine combination, we will need a high-pressure fuel pump. We could have installed an in-line fuel pump, but we prefer to install an in-tank pump for quieter operation.

Why The Sniper Retrofit?

Rat Rod Fuel Pump 19-350

The Holley Sniper Retrofit Fuel Module is able to support 700 horsepower for a fuel-injected engine, or 900 horsepower for a carbureted engine. It will also install into virtually any fuel tank. Match made in Heaven, if you ask us!


We ordered up a Holley Sniper Retrofit 340 LPH Fuel Module with return capability (p/n 19-350). This setup allows you to install a high-pressure fuel pump into virtually any fuel tank, including the one that’s in our T-bucket. Our tank is just a cylinder that mounts in the back of the vehicle, above the rear suspension. It was originally designed to have a feed line from the bottom of the fuel tank, feeding a traditional engine-mounted fuel pump.


The Holley Sniper Retrofit pump is one slick unit. The reality is that it is just a matter of drilling a hole, assembling everything and then hitting the road. The supplied pump is capable of providing fuel for up to 700 horsepower with fuel injection, or 900 horsepower on a carbureted application.

The Installation Process

Rat Rod Fuel Pump the tank

We initially had concerns about how well the Retrofit module would work with our T-bucket's cylindrical fuel tank. After checking our measurements, were were pleased to find that we were within tolerances.


One concern we had before installing the Sniper Retrofit pump was the cylindrical shape of our tank. Our concern was that at the edges of the module we might see a leak, due to the cylindrical shape of our tank versus the rather flat mating surface of the pump module. Reading through the instructions, though, we saw that there can be up to .28-inch amount of uneven surface and the pump will still seal. We determined that we are right at that number with some measuring, so we shouldn’t have any issues. However, if the ribs on your tank are deeper, you’ll need to use a sealer, such as Dow Corning 730 fluorosilicone RTV, between the foam gasket ring and the tank surface.


The first step was to drill the required 3.25-inch hole in the tank. We ordered a hole saw and went to town. However, the bit just wouldn’t cut through the tank! Our tank is thicker than we were expecting and the hole saw was just not going to make an impact. We ended up biting the bullet and used our handy-dandy plasma cutter to cut the hole in the tank.

With the hole opened up, we went ahead and measured from the top of the tank to the bottom. The goal here is to trim up the supply and return hoses on the module along with the hanger itself, so the pump sits at the bottom of the tank. This step is crucially important, so take your time and measure twice.


You want the sock on the bottom of the pump lightly touching or almost touching the bottom of the tank to ensure that it will get fuel, even when the tank starts to run low. After verifying our math to make sure our measurements would work, we trimmed everything up.


Rat Rod Fuel Pump measure the depth

A very crucial step in the installation process involves measuring the depth of the tank for the supply and return hoses. The goal is to have the sock of the pump resting on or just at the bottom of the fuel tank so that it can still siphon fuel up to the pump, even with a lower fuel level.


After trimming the supply hose, we used a heat gun to slightly warm up the hose. This allowed us to easily slip the pump into the hose end. We then installed the trimmed down hangar and then used the supplied hose clamps to hold it all together.


Before we could slide this into the tank we needed to add the sock to the end of the pump, which uses a serrated washer to hold it into place. We also slid the foam gasket over the entire assembly.

With the pump officially in the tank, we needed to plumb everything up. The pump housing has three different 1/4” NPT female ends: one for the supply line, one for the return, and one for the vent tube. We are still a little way off from plumbing up the rest of the fuel system on the T-bucket, but we plan to adapt these fittings into Earl’s -6 AN fittings at the module before plumbing the rest of the system with Earl’s fuel hose and fittings.


Rat Rod Fuel Pump installed

Here is the Retrofit module, installed. We will finish up the fuel plumbing between the module and the LS up front with Earl's fittings and hoses. The wiring for the pump is simple: the black wire needs a solid, clean ground and the red wire is your 12-volt power feed. We recommend that you use a relay that gets power directly from the battery for best results.


The electrical is pretty simple for this pump: The black wire needs to go to a good ground and the red wire is the power supply. However, you don’t want to connect the red wire to any ordinary switched 12-volt supply. Be sure to incorporate a relay that gets power directly from the battery for the best performance and to help ensure trouble-free miles.

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