The Sniper EFI Stealth 4150 Supports Big Power But Remains User-Friendly
For most semi-savvy car enthusiasts, unless you're a died-in-the-wool carburetor guy, installing and setting up an EFI system can be one of the simplest and most rewarding upgrades to a classic car. In the past, this 1955 Chevy has had a mild 350 small block with a single plane, four-barrel intake topped by a Quadrajet that we were always trying to dial in properly, followed by a 327ci with Tri-Power that looked straight out of the early 1960s, but with similar situations. We eventually replaced the 327 with a freshly-built stroker motor topped by an early throttle body EFI with forced induction. It ran like a scalded cat, until it hit the wall due to the limits of the small injector size of that early unit. It remained that way for years, until we decided that it was time to tear down the wall and join the modern world.
Since our 377ci engine was dressed to appear as though it was built that way in 1955, a tuned port EFI system was out of the question. We needed an option that would fit under a stock-style air cleaner and not look completely out of place, given our early aesthetic. But while it needed to look the part, we also wanted to cure our fuel limitations.
To get down to brass tacks without over burdening the topic, our original throttle body was equipped with four 80lb/hr fuel injectors and hit maximum duty cycle (100%) at just under 5,000rpm, as witnessed on the dyno. That meant that running the engine over 4,000rpm or so would put our engine in a precarious position where it could suffer from a lean condition. On a naturally aspirated setup, that would be enough to warrant your attention, but in a forced induction scenario, the idea of encountering a lean condition, under boost and acceleration, was a situation we wanted to desperately avoid.
While we could sit down and calculate the fuel load necessary for our particular application to yield an appropriate duty cycle, the engineers at Holley have made selecting an appropriate system for our engine easy, thanks to the extensive Holley product line that covers a wide range of power levels. Given that we hit the proverbial fuel wall at 578hp / 620lb-ft., we knew we needed a system that could eclipse those numbers, with some room to spare.
With all that said, it made the most sense to choose one of Holley's newest EFI kits, the Sniper EFI Stealth 4150. Based around the original architecture of a 4150 4-barrel carb, the Stealth contains EIGHT 100lb/hr fuel injectors (that's over three times our original throttle body!), capable of supporting up to 1,250hp. And yet while the Stealth can support some big numbers, it doesn't take any special equipment, tuning, or capabilities to get the system installed, and up and running. Using the provided handheld controller, an intuitive wizard aids the end user through a series of questions to get the proper information loaded into the computer (number of cylinders, engine displacement, target idle speed, camshaft type, etc.) before it then loads a base map tune automatically, preprogrammed by Holley's engineers. From there, the system can be operated in a "closed loop" configuration, resulting in a self-learning / self-tuning situation that adjusts on the fly, without the need for expensive dyno tuning time.
The result truly speaks to the state of the hobby when it comes to the technology that's finding its way into our classic cars. Twenty years ago, the thought of a DIY EFI installation without the need of a laptop or expensive tuning was truly a pipe dream. Today, not only is it a reality, it's becoming commonplace. Upon completion of our Sniper EFI Stealth kit, checking fuel pressure, and ensuring that we didn't have any fuel leaks, we ran through the Sniper's Initial Wizard and had our small block fired up faster than you could say "main jet swap"! And with the system up and running, just like the song, you know who came out and said, "honey, take me for a spin". As it turns out, that's exactly what we needed to do!
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