One key to a successful electronic fuel injection conversion is, and always will be, to employ a high-quality fuel delivery system. If constant, pressurized fuel can’t make it to the injectors the best EFI system in the world will perform poorly. This may sound simple enough, but the devil is—as they say—in the details, and the fine points will make or break a good installation.

It is in Holley’s best interest as a fuel injection manufacturer to come up with a quality system that will work under grueling street conditions and high-g loads. They offer a few different universal fuel tank conversion kits and the HydraMat filter/pickup works very well. But the best situation is to create a fuel tank with a built-in fuel reservoir and then make those tanks for the popular performance cars like Camaros, Chevelles, Corvettes, Novas, and even trucks.

That’s exactly what the Sniper fuel delivery system is all about. The kit comes with a Holley performance “pump-on-a-stick” system with a specific flange to mount the pump assembly inside a large reservoir located at the front of the tank. Alongside the pump assembly is a fuel level float assembly to drive the gas gauge.

Our plan was to upgrade our LS-powered Chevelle from a carburetor over to EFI using Holley’s HP EFI ECU to transform this Chevelle over to 21st century fuel control. When Holley released the Sniper line with a dedicated fuel tank for this conversion, it became a moral imperative to make the conversion. Our old system used an externally mounted fuel pump and stock tank pickup with a return back to the tank. It worked fine for our carbureted application, but it would have been inadequate for the constant EFI fuel pressure requirements.

Our new engine is an iron 6.0L LS with TFS heads that recently came off the dyno making 556 hp. The standard Sniper system uses a 255-lph (liter per hour) pump that is rated to deliver up to 550 hp worth of fuel at EFI pressures. Since one of the possible upgrades would be an NOS nitrous system controlled by the Holley HP, that entry-level pump capacity was going to be insufficient. Luckily, Holley offers an optional 400-lph pump intended just for gasoline that bumps the rated capacity to 750 naturally aspirated hp, which fits perfectly into our upgrade plans.

Perhaps the most important advantage to an in-tank pump is that the inlet to the pump is always submerged in fuel and does not have to “pull” fuel from the tank to the inlet as with an externally mounted pump. A standing column of fuel above an in-tank pump uses the weight of this fuel to push fuel into the inlet, improving pump efficiency. Plus, since the pump is submerged in fuel the pump will run much cooler, which improves durability.

Our current fuel delivery system was more than 10 years old and used older, rubber-lined braided steel hose. Because this car often sits for months at a time between test sessions, rubber fuel hose can quickly become brittle after alternating between wet and dry sessions. This drying cycle takes a toll on any rubber-lined fuel hose. We added a length of hard line, which helps, but the real solution was to replace the flexible hose lengths with a more durable material.

For years, the OEs have been using what is often referred to as plastic fuel line. The material is actually carbon-infused PTFE. This acronym stands for Poly-Tetra-Fluoro-Ethylene, which has also been known by the brand name Teflon. This material is extremely resistant to all types of fuel—even methanol and nitromethane—and if not abraded or exposed to open flame, offers an extremely long lifespan. Because of its strength and wall thickness, the material is somewhat stiff, necessitating a wide bend radius to prevent kinks.

Holley’s UltraPro hose uses a convoluted, or corrugated, wall construction that makes this hose both light and very easy to route with a very tight bend radius. When fuel is pushed through standard, white PTFE hose, the material is not a conductor so static electricity can build up on the line and cause pinhole leaks. UltraPro hose is carbon-infused (black), making it a safe conductor so there’s no chance of a buildup of static electricity.

Make no mistake, the UltraPro hose and its specific fittings are expensive, but we’re talking about a high-pressure fuel delivery system, which demands we make it as safe as possible. Investing in the Earl’s hose and fittings is likely to make this the last fuel delivery system this car will need. Plus, it is completely compatible with different fuels, such as E85, should we decide to experiment with that fuel in this car.

With this relatively simple installation, we now have a very nice in-tank fuel delivery system capable of feeding 750 hp that looks nearly stock when mounted in the car, and will work flawlessly with our new EFI system. It’s much cleaner than our previous effort, and that production-style fuel pump will last for years. Other than more horsepower, what more could you ask for? CHP

A self-contained EFI fuel tank like this Sniper system makes for a clean installation and a far more efficient pump assembly.

This is the Sniper steel tank for our Chevelle upgrade. It really is as nice as the photo shows. Inside the tank is a reservoir designed to retain fuel around the fuel pump. This will work fine perhaps to under an eighth of a tank where there might be issues where the fuel could move away from the pickup. The Sniper tank was roughly one inch deeper than our stock tank to allow mounting the in-tank pump. The tank also comes with new straps to accommodate the 20-gallon capacity.

This is the pump and float level assemblies that come with the tank. This kit uses the larger 400-lph pump that will feed upward of 750 EFI horsepower. Holley also offers a 450-lph pump that will accommodate E85.

This is the optional 400-lph pump for this system. It’s hard to image that a small pump like this can generate more than enough fuel and pressure to feed 750 hp.

The pump bracket must be custom-fitted to each tank. This requires accurately measuring the depth of the system at the mounting location. Our depth was 6 5/8-inches and we set the pump depth to place the inlet just off the floor of the tank.

We installed and trimmed the float level assembly for the fuel level gauge and positioned it so the internal reservoir would not interfere with float operation. The float level lid installs in only one position, so we had to rotate the entire assembly to clear the reservoir.

Here is the entire pump assembly about to go in the tank for the final time. We tightened the bolts in a star pattern to make sure the lid was evenly secured to the tank.

With both the float and pump assemblies in place, we used Earl’s 1/4 NPT to -6 male AN adapter fittings to connect the pressure outlet and return lines. There’s a vent tube in the tank as well as another in the pump assembly. The kit supplies a Y-fitting to connect both to an external vent using 5/16-inch hose.

This is the anti-siphon rollover valve that we will connect to the vent and locate externally above the tank. An internal check ball prevents fuel from leaking out the vent should the vehicle roll over.

This was our original fuel system using an external pump and pre-filter assembly mounted on an aluminum bracket just ahead of the stock tank. Unfortunately, this positioned the system very close to the rear axle housing. All of this and the stock tank were removed.

We also converted to new Holley fuel lines that will allow us to use virtually any fuel—including E85. Earl’s convoluted UltraPro PTFE -6 hose is the best choice for fuel compatibility and durability. The hose does require specific fittings.

To assemble the Earl’s UltraPro hose, first pull back the outside cloth covering and slip the tapered end of the silver ferrule over the inner hose, extending a small portion of the hose past the end of the ferrule. Trim the inner tube flush with end of the ferrule with a razor blade and then screw the hose end together.

Since the in-tank pump uses a pre-filter, the only other addition for this system was a Holley filter downstream to ensure all the impurities have been removed. This is a 100-micron stainless filter, but a 10-mircon is what you want for downstream filtering. The smaller the micron number, the finer the filtering potential. A 10-micron filter will capture anything larger than 0.0004-inch!

Holley offers a universal pump conversion using the same fuel pump with a more substantial aluminum lid that will seal to the top of the tank. The only limitation would be the minimum tank depth required. In our case, our Chevelle tank wasn’t deep enough to accommodate the Sniper in-tank conversion—necessitating the entire Sniper kit.

Here’s the final installation with the tank in place. This is a much cleaner installation compared to an external pump. In our car, this did require narrowing one section on each 3-inch tailpipe as the larger tank hit the pipes, but that was the only hiccup.

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