Despite EFI origins, LS motors actually love carburetors. If one is good, then two is even
Modern Mouse has a busy life. Just a few short weeks ago, our 5.3L LS-based 383 stroker engine was sporting a massive Whipple supercharger and pumping out over 800 hp. Superchargers are capable of some serious power, but the fact that the big numbers came from less than 10 psi of boost made it all the more rewarding.
Before that, we saw additional displacement and a wide variety of different bolt-ons. Having run through cams, intakes, and a couple of power adders (oh, there will be more), we decided it was time to cater to the carbureted contingent.
Given the popularity of LS engines as swap candidates in early muscle cars, it seemed only natural to take a look at carburetors. While a number of carbureted intakes are currently available for LS applications, Holley recently introduced a trick dual-quad intake for LS engines equipped with cathedral-port heads. Since man does not live by fuel injection alone, we decided it was high time to equip Modern Mouse with some old-school induction.
As much as we love the original small-block, it has just been so easy to make power with Modern Mouse. So far, we have easily exceeded 500 hp in normally aspirated trim, and topped 800 hp with boost. More than just big (one-time-only) dyno numbers, these came as realistic and wholly usable outputs that could be enjoyed on a daily basis. We demanded no less from our carbureted intakes, despite the fact that dual-quad induction systems are often chosen on looks alone. It's hard to argue with the performance and reliability of a single carb on any engine, but they certainly rank behind a trick dual-quad setup when it comes to the all-important "wow" factor. The problem with multi-carb induction is that they often lag behind the single-carb setup in terms of driveability and performance. For some, looking fast takes precedent over actually being fast, but what is wrong with wanting both?
1. The subject of our test was the new Holley mid-rise, dual-quad intake designed for cat
To illustrate that it is possible to offer both form and function, we took Holley up on its offer to test its new dual-quad intake system. Designed to fit LS applications with cathedral-port heads, the new mid-rise, dual-quad intake was listed for LS engines up to 427 cubic inches with an effective operating range to 7,000 rpm. The mid-rise design positioned the intake between a standard low-rise, dual-plane and a dedicated (high-rise) tunnel ram. Holley now offers a dual-quad tunnel ram for rectangular-port LS3 applications, which we have tested with excellent results.
Having run that tunnel ram on a stroker LS3, we were anxious to see what the mid-rise design had to offer on our 383 stroker. Our one (very minor) complaint about the intake involved carburetion. Holley designed the intake to receive a pair of 4160 carbs or (of all things) Carter AFBs (or Edelbrock equivalents). Some feel it would be sacrilege to run anything but Holley carbs on a Holley dual-quad intake, but that said, we must admit that the induction system worked extremely well with the pair of 390-cfm 4160s.
Rather than compare the dual-quad intake to the FAST (or other) EFI system, we decided to select a typical carbureted single-plane intake. We figured that the choice would be less about carburetor versus EFI than different carbureted intakes. We also wanted to see how well the dual-quad induction stacked up against a known entity. For this test we selected what is considered by many to be the mainstay of single-plane manifolds, the Edelbrock Victor Jr. intake. We know from experience that a single-plane intake will usually offer impressive top-end power but often sacrifice low-speed torque. For most street applications, the dual-plane is a better choice thanks to improved torque through most of the rev range, but it is hard to top the single-plane intake for peak power.
2. The dual-plane design is evident in this photo. Note that four of the ports are fed by
3. Like the factory LS, the Holley intake utilized dedicated O-rings (included in the kit
4. The Holley dual-quad was combined with a pair of 390-cfm 4160 carburetors. Though they
5. The inline position of the carburetors made carb linkage a snap. We used a pair of mou
6. The carbs and intake provided the fuel, but our LS stroker still needed ignition. MSD
7. For our carbureted intake test, Modern Mouse was equipped with a set of 1-3/4-inch hea