Four-Barrel Carburetor to Eight-Barrel Swap - How It Works

Swapping out that four-barrel for an eight-stack induction can net massive performance. Inglése explains how it’s done.

Stephen Kim Oct 25, 2012 0 Comment(s)
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Not until recent years did Europeans figure out the benefits of cubic inches. During the ’60s, fabled brands like Ferrari piddled around with weenie-displacement V-12s no larger than a typical American straight-six. Even so, what they lacked in cubic inches they made up for in spades with exotic good looks. Popping the hood of Maranello’s finest revealed 12 Weber carburetors sitting atop a dozen polished throttle stacks. Aesthetics were just part of the equation, as the basic nature of having an individual throttle stack for each cylinder netted massive gains in low-rpm torque over a typical common-plenum intake manifold. Cars like the Shelby Cobra represented one of the first domestic applications of a Weber induction system, and since then hot rodders have been going gaga over eight-stack induction systems.

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Good looks aside, common sense says that having eight times as many carbs can give you eight times the headaches, and Webers have earned the unenviable reputation for being little devils to tune. Well, that was then and this is now, as companies like Inglése have taken the guesswork and potential pitfalls out of adapting an individual-runner induction system to your Bow Tie. It offers a full line of bolt-in-and-go eight-stack intake systems for big- and small-block Chevys, as well as LS applications. To find out what’s involved with installing an IR intake, and to learn the science behind why they can often stomp a four-barrel-type induction system into submission, we had Jay Adams of Inglése explain it all to us.

Individual Runners For the Street

Back in the late ’70s and early ’80s, hot rod builders were looking at exotic ways to make their engine bays more visually stunning as compared to the typical 14-inch round chrome air cleaner. Jim Inglése, being familiar with the hard-core Weber carbureted racing induction systems associated with Shelby Cobras and road racing cars of the ’60s, saw an opportunity to combine that look while taming them for street use to fill this void. Inglése adapted these exotic individual-runner induction systems to fit domestic V-8s, including the small- and big-block Chevy and LS-series motors. Today, Inglése manufactures its own intake manifolds and offers induction systems with Weber carburetors or EFI.

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Eight-Stack Basics

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The intake runners on a typical single- or dual-plane intake manifold share a common plenum, while the runners in an individual-runner intake manifold do not. This arrangement offers several performance advantages. For many years, individual-runner induction systems got a bad rap for being too hard to tune for street use, but that’s an unfair cross to bear. Once you understand the capabilities of an IR system, and what it likes, they’re quite tunable, driveable, and capable of being very docile in many applications. In an IR system, each cylinder has its own dedicated column of available air since it doesn’t have to share a common plenum with adjacent cylinders. How that air is used to make power in a specific application determines how well the engine will respond to various applications. In addition, Inglése has also designed manifolds that share a limited common plenum area in order to provide a consistent vacuum signal to the MAP sensor, or allow for brake vacuum, without hampering the performance inherent to an IR design. Ultimately, common-plenum and individual-runner induction systems each have their place, but require specific engine tuning and camshaft design considerations. As part of the COMP Cams family, tapping into COMP’s leadership in the valvetrain arena really makes a shining difference for tuning and designing IR induction systems these days as compared to previous years.

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