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How to Make 900+ Horsepower with a Blow-Through Holley Super Sniper EFI

Author: Evan Perkins | Photographer: Mark Gearhart | 10/01/2020 < Back to Motor Life Home

Folks, we are in the golden age of horsepower. There are factory muscle cars rolling off the showroom floor with 800+ horsepower and even a mundane, new minivan is rocking nearly 300 ponies under its utilitarian snout. With all of the advancement in modern engine performance and output, it’s fair to say that our humble small blocks and big blocks have benefitted in tandem. The aftermarket has continued to embrace these muscle car mills and coaxing big power from them is easier than ever before.


Holley Super Sniper 4150 Stealth

The Super Sniper Stealth contains 8, 100lb-hr injectors and can support 1,250 horsepower and 21.5psi of boost making it ideal for blow-through or draw-through applications. The "Stealth" version of the Sniper is designed to look like a carburetor for those that desire the benefits of old-school looks with modern fuel-injected performance.


Enter Holley’s Sniper EFI, a completely self-contained fuel injection system–ECU, injectors, sensors, and all– with modern EFI performance that literally bolts to the intake in place of carburetor. Sniper EFI is offered in multiple styles and configurations, but it’s the Super Sniper that’s garnered the most attention from power-hungry gearheads. With eight, 100lb-hr injectors inside, and a 2.5bar MAP sensor, the Super Sniper can support 1,250 horsepower and boost pressures up to 21.5psi.


To demonstrate the capabilities of the Super Sniper, we teamed up with ProCharger superchargers and bolted a Super Sniper Stealth to a boost-ready small block. Super Snipers are available in 4150 flange, 4500 flange, and in the 4150 Stealth variant used for this test. The “Stealth” version of the Super Sniper is designed to have a subtle carb-like appearance that’s ideal for applications where factory-esque appearance under the hood is desired.

Under the valve covers, this small-block isn’t anything outrageous. It features a BluePrint engines, 1-piece rear main seal block stuffed with forged rods, crank, and pistons, and a COMP Cams hydraulic roller cam that specs out to a moderate 236/242º at .050-lift. The cylinder heads are an ultra-affordable pair of Brodix IK210's and a Holley Strip Dominator intake ducts the fuel-injected air into the cylinders. The engine does feature an over-square bore/stroke of 4.155in x 3.48in for a total displacement of 377ci. This combination allows for a decent displacement and a longer connecting rod(6.000in vs the factory 5.700in) while still allowing for a thick piston crown that can tolerate the heat of big power and boost.

The blower of choice for this test is a ProCharger F-1A-94 which is rated for up to 1,300 horsepower. We bolted it onto our small-block with the supplied aluminum bracketry and piped it to our Super Sniper Stealth with the supplied aluminum elbow and rubber couplers. This kit was designed for carbureted applications, but due to the carb-like qualities of the Sniper, it bolted up just the same. With the engine complete, we headed down to Westech Performance to see just how much power we could crank out on the engine dyno.


On the Dyno


Sniper Westech Dyno

Once on the dyno, the engine fired up easily with a few quick clicks of the Sniper handheld interface.

Once hooked up to the dyno, we utilized the Sniper’s handheld setup wizard to enter a few basic parameters on the engine and fire it up. While all Sniper EFI systems are self-learning capable, for big power applications such as this, it’s always recommended to have a professional calibrator tune the system with the free, downloadable software [available here]. When boost, power, and high RPM are involved, the margin of error for tuning shrinks considerably so the engine was tuned by sweeping it through different loads and RPM bands to progressively build a safe tune. We also had three different pulleys handy for the ProCharger so that boost could be added incramentally as the tuning progressed.

Westech’s Ishmael Candia deftly handled tuning of the Super Sniper while Steve Brulé worked the dyno, slowly ramping up the RPM and tune in harmony until it was time to make full power pulls. With the first (largest) supercharger pulley queued up the small-block rewarded us with an effortless (and lucky) 777 horsepower at 6,500rpm. Boost from the ProCharger came in at 8psi. Despite the short stroke and rev-happy rotating assembly, the engine experienced valve float at 6,500rpm due to the hydraulic roller cam and relatively soft valve springs. 6,500 became the ceiling of the pulls for the remainder of the dyno session. The second pull, with a slightly smaller pulley, turned the blower faster, producing 11psi of boost and 840 horsepower. On our third series of pulls, Brulé added higher octane race fuel to the tank as some additional tuning margin and we let the blown engine sing once more with the final, smallest pulley. 14psi of boost later, the 377ci engine belched out 902 horsepower, a whopping 2.39 horsepower-per-cubic-inch. Had the engine been equipped with a solid roller camshaft and more valve spring pressure, Brulé was confident the power would have climbed into four-digit territory around 7,300rpm. By the looks of the dyno curve with no end in sight, it's hard to disagree with that seasoned dyno wisdom.


super sniper dyno results

There you have it: over 900 horsepower from a bolt-on blower, bolt-on EFI system, and nothing-special small-block Chevrolet engine.


When it comes to the hierarchy of fuel injection system styles, the top-tier Holley offers is always going to be multi-port fuel injection (MPFI). By placing the injector directly in each cylinder’s intake ports, there is little-to-no variation in cylinder-to-cylinder air-fuel ratio. Much like with a carburetor, the Sniper’s throttle-body-injection inevitably allows the manifold to exert more influence over the path air-fuel takes to reach each cylinder.


However, throttle-body injection is not without its own unique set of advantages. By introducing fuel into the inlet charge further from the port, that fuel has more time to evaporate before combustion occurs. This latent heat of vaporization acts like a chemical intercooler and helps to drop the temperature of the incoming air-fuel.


super sniper stealth blow-through

For this test we used a carb-style hat to duct boost directly from the ProCharger to the Super Sniper in a blow-through configuration. This would work just as well with a turbo, or the Sniper can be installed in a draw-through application such as a roots-style supercharger.


In addition, no fabrication was required to build a supercharged, 900 horsepower engine. The Super Sniper Stealth bolts to any 4150-style carburetor flange, takes only 4 wires to hook up (RPM signal, battery positive, battery negative, and ignition 12v), and unlike a MPFI system, does not require the hassle or expense of fabrication should the engine lack fuel injector/EFI sensor provisions. As always, it’s about selecting the right tool for the job, but unequivocally the Super Sniper delivers serious bang for the buck and is capable of making some seriously wild, boosted power!

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