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When General Motors first unleashed the LS7 on the motoring public back in 2006 under the hood of the then-new C6 Corvette Z06, it was clear that GM had produced an engine that would become a modern legend. The largest displacement small-block ever produced en masse, the LS7 boasted the same 427 cubes as the iconic power plants from the muscle car era that had provided motivation for big block C2s and COPO Camaros from back in the day.
But the LS7 is noteworthy for more than just a number. It’s a thoroughly sorted OHV power plant that loves to rev to its 7000 RPM redline (or significantly higher with a few well-chosen modifications), a hand-built testament to the enduring relevance of pushrod engines in modern times. So it should come as no surprise that mill has proven quite popular since its debut, both in its factory use in the Z06 and later in the Camaro Z28, as well as a crate motor that was offered from Chevrolet Performance.
The LS7's race-inspired engineering makes it a great swap candidate for builders that are looking for a rev-happy modern engine.
Now more than ever before, the LS7 is finding new homes in engine bays that it was never designed for, a trend that has presented some interesting challenges for builders looking to make this unique LS work in their project.
If you’re one of those folks and you’re hitting a roadblock when it comes to the intake manifold, fret not – Holley Performance has you covered with their single plane EFI intake. Designed specifically for Gen III LS engines running LS7 cylinder heads, this low-rise manifold offers both pragmatic and aesthetic benefits, making a particularly attractive option for hot-rodders. Let’s take a closer look at the details.
“One of the primary objectives here was to create a solution for the retrofit street/strip projects,” explains Holley Performance senior design engineer, Jim Dralle. “GM did a tremendous job designing their manifold, obviously. But when a builder gets an LS7, which is a bit more of an investment than an L92 or something like that, either when pulled from a Corvette or bought as a crate engine, we’ve noticed a few potential scenarios tend to pop up.”
The manifold's low-profile design ensures that it will fit a variety of different vehicles with minimal hood modifications required.
The first of those is an effort to achieve some aesthetic continuity, Dralle says. “Everybody’s familiar with a 4150 flange, and there’s something comforting about that, I think. You open the hood and there’s a traditional circular air cleaner on top of the engine. If you’ve got a late 60s or early 70s Chevelle, you might not necessarily want to pop the hood and see an engine that might look out of place. They want the benefits of a modern engine, but also they want it to look like it belongs there.”
Dralle also points to installation concerns as another primary driver to develop this single plane intake for the LS7. “Throttle linkages, fuel lines, air cleaners – all those things are really comfortable with that standard four barrel flange. It puts everything where you expect it to be if you’re approaching this from a hot-rodder’s standpoint.”
The design allows for an air cleaner to mount atop the engine like a traditional carbureted setup, in turn providing some of the visual appeal of an old school power plant.
Although this low-rise LS7 intake manifold was particularly notable for its packaging and visual benefits when it first debuted a few years ago, development engineers also wanted to make sure that the part could deliver the kind of performance that builders have come to expect from Holley.
“It’s all about what a particular engine wants,” Dralle says. “And, even as good as the cathedral port and LS3 port are, the LS7 cylinder head is just another step above that, so you need to design around what that offers. With the LS7 you’re getting bigger bore sizes and more displacement to work with, and it definitely affects your cross-sectional areas and those kinds of things when you’re designing an intake manifold. There’s a lot of external factors that have to be considered when designing the air passages that go into an engine, but there are two things that are of highest importance. You need the flow velocity to be correct – you don’t want it to be too high or too low, and you want it to be as low-restriction as possible.”
The runner layout and constant cross-sectional area have been designed to deliver a broad torque curve that makes power down low, and continues to do so all the way to 7,000 RPM.
Achieving those characteristics in a low-rise design requires an extra dose of creativity, he tells us. “Sometimes it becomes a bit of a plumbing exercise. You know what you want to do, but you are also working under some very specific packaging constraints, so you do everything you can to minimize any potential compromises in a given situation. And of course, you have to be able to cast it as well, so that all plays into the final shape.”
Dralle points out this low-rise single plane manifold will tend to yield a powerband that are favorable to street and strip cars into which LS7 engines are being installed. “This manifold will run well everywhere, really shining in the RPM range, where the torque is being used on the street, tending to give a broad, smooth power curve.”
Also adding to the manifold’s versatility is that, while EFI bosses have been drilled into the manifold, they can be easily plugged to make this part work with a carbureted setup if a builder chooses to go that route. “The plenum itself was designed to work with a carburetor, to work with a wet system,” Dralle says. “And of course, you also have the option of going with a Sniper-type of fuel injection system, or the various throttle body fuel injections that Holley does. There’s some great simplicity and modularity from that aspect, too.”
The manifold can run a standard rail-fed fuel injection system, or with the injector ports blocked, any of the Holley throttle body setups, like the Sniper, or even a carbureted setup.
Holley’s LS7 carbureted-style single plane EFI intake manifold is made from aluminum, which both aids the old school look and also provides builders with more finish options that they’d otherwise have with a composite piece.
The manifold is available directly from Holley in either a cast finish or a durable black powdercoat finish.
“With a plastic manifold, you’re pretty limited on what you can do. With this intake you can powder coat it, polish it, do a satin finish – whatever you want.”
And it follows in Holley’s tradition of producing parts that are a cut above. “We’re very capable of delivering a quality product,” Dralle adds. “From engineering to manufacturing, Holley’s has the resources, and has been around long enough, to really understand how to deliver in those respects.”