Multiple carbs is a notion deeply imbedded in our psyche, calling back to the days when hot rodders measured credibility on how many Stromberg 97s could be made to fit on the engine. The appeal of multicarbs was reinforced by Detroit, with dual-quad and triple two-barrel inductions appearing in the '50s. They gained even more popularity during the escalation of the factory musclecar wars of the '60s, when this induction layout became forever etched into the minds of the performance-minded with a dizzying array of three-carbed FE-Fords, Pontiacs, GTOs, Six Pack Mopars, and 427 Corvettes.
Three-deuce inductions, as well as the early dual-quads, simply came about as a way of fulfilling a need for airflow. In those days, the limited selection of four-barrel carburetors was hampered by relatively short capacity when considering high-power ambitions. Multiple carburetors were a practical way to go fast. Today, we have four-barrel carbs of capacities that will quench the airflow needs of the mightiest engine combination, but the desire for multicarbs remains. It's the look, the presence, and the voice of nostalgia that drives this desire today. Barry Grant set out to fulfill that desire with the SixShooter line of triple two-barrel inductions for nine different musclecar V-8s.
Most of these systems are not based on a rehash of the OEM components of previous decades but are all-new designs that begin with a dedicated cast-aluminum intake manifold bearing a conventional two-plane configuration. In combination with a trio of mechanically actuated Demon two-barrel carburetors, the SixShooter is the first new induction of its type in years. It is designed as a complete package, with carbs operated via a progressive mechanical linkage featuring adjustable spherical rod ends and an attractive billet-aluminum and stainless steel fuel log that unobtrusively feeds the row of carbs from a single forward fitting.
Each carb has a capacity of 250 cfm, with the center carb in exclusive operation under low-throttle angle conditions. Both the idle circuit and electric choke operate at the center carburetor only. The outboard carbs serve as the secondaries and start working at a predetermined throttle angle as the progressive linkage is leaned on. Finally, the system comes with a polished-aluminum air-cleaner assembly, complete with a Rush gauze/wire-mesh air-filter element. For small Chevy applications, the complete system runs about $2,400.
Evaluation and TestingLured by the SixShooter's exotic looks and a desire to cut away from the four-barrel herd, we looked toward this system to provide the induction for our 383 street small-block. Originally built as a stout street engine, it was assembled with a relatively aggressive Comp Cams Xtreme Energy XE294HR hydraulic roller camshaft and features World Products' Motown 220 iron heads and a compression ratio of just a tad over 10:1. The induction system consisted of a Mighty Demon 750 carburetor on an Edelbrock Performer RPM Air-Gap intake manifold. Although the induction represents simplicity in itself, this combination has proved unassailable in outright power output for engines of this type and power level.
Were we expecting to unleash beastly power gains with a change in induction? Frankly, no. In fact, we were prepping the engine to serve duty in daily-driver mode, and among the changes planned, we intended to unwind the camshaft to a mellower grind. So does that make us poseurs or heretics to the gospel of power? Maybe, if intending to drive a three-deuce-equipped, 400-plus-horsepower street machine makes it so.
To weigh the pros and cons of the choices involved in our engine reconfiguration, we trucked the small-block to Westech Performance Group with dyno testing in mind. We'd baseline the current configuration-four-barrel and big cam-with our SixShooter and street-friendly stick waiting in the wings. That array would give us the opportunity to test four distinct configurations and assess the changes in power as well as idle quality. What is the right combination? Consider your own application and goals. For this installation, we were looking to achieve frustration-free driveability and road manners while achieving good overall output and presenting something with a look under the hood that's a cut above the crowd.
Central to the plans was the camshaft. Our milder street cam, like the baseline cam, is also a Comp hydraulic roller, though it's 25 degrees shorter in overall duration than the more radical piece it was to replace. Idle quality and good manifold vacuum without suffocating power output below a 6000-rpm power range were the targets. With the relatively high compression ratio and short cam duration, we broadened the lobe separation angle compared to the baseline cam in hopes that the resultant later intake-closing event would reduce cylinder pressure a tad, thereby helping keep detonation in check. Moreover, the wider lobe separation will result in less overlap duration, which will also improve idle quality and vacuum.
The ResultsAimed at stout street performance, we found that our baseline combination of big cam and four-barrel delivered 475 hp from 6,000-6,300 rpm and 467 lb-ft of torque. Along with it came a noticeably agitated lope, and, after tuning, we achieved around 10 inches Hg of manifold vacuum. For a street bruiser, it's a combination that is right on target. Here, if outright power is the primary goal, the four-barrel had a distinct edge over the SixShooter. It came out of the hole with a slight advantage at the bottom end and spread that to 20 hp at the peak.
In street-cruiser mode, we swapped to the smaller Comp cam and weren't surprised by the significant change in idle quality. Twenty-five degrees of duration is not a subtle change. With the tamer cam, the aggressive lope of the 383 was muted to a steady rhythm, and idle vacuum soared to 16 inches Hg, a gain of 60 percent. The shorter 'shaft dropped our usable rpm range by 500 down to 5,800 rpm from the lofty 6,300 achieved with the hotter combination. We also observed a distinct shift of the power curve. The bottom-end torque rose significantly below 3,900 rpm-just compensation for the power given up at the top. Here again, we found that in outright power, the four-barrel Demon and Air-Gap arrangement held tenaciously to the power advantage exhibited with the larger cam, though the spread between the two had shrunk to 8 hp, peak to peak.
The SixShooter does the job of enhancing the wow factor on the engine, but it'll cost you a few horsepower compared with the unbeatable Air-Gap/750 four-barrel combination. Is individuality worth it? We still see guys running Strombergs and flatheads with pride just for the intangible of old-time appeal, so the choice is, as always, up to the individual.
SixShooter ApplicationsThankfully, Demon makes SixShooters for more than just the small-block Chevy. They cost $2,515.75 racer net. The FE kits, you'll notice, do not come with intake manifolds. They're designed to bolt right on to original three-deuce manifolds, which aren't as hard to find as the other makes. Hence, they cost less, at $1,794.40 racer net. Not on the list but next up is a SixShooter for Mopar 383-440 engines.
PN Application 7500 Conventional small-block Chevy 7505 Vortec-headed small-block Chevy 7510 Big-block Chevy (oval ports) 7515 Big-block Chevy (rectangular ports) 7520 {{{Pontiac}}} 326-455, '65-'79, except Ram Air IV 7530 289-302 {{{Ford}}} 7540* Ford FE with plain air-cleaner lid 7541* Ford FE with ribbed air-cleaner lid Coming Next* Mopar 383-440*Not a complete kit. Does not include manifold.
Camshaft Specifications Big Cam Small Cam Grind number XE294HR XR269HR Type hyd. roller hyd. roller Gross duration intake (deg) 294 269 Gross duration exhaust (deg) {{{300}}} 276 Duration @ 0.050-inch intake (deg) 242 218 Duration @ 0.050-inch exhaust (deg) 248 224 Intake lift (1.6:1 rocker ratio) 0.540 0.495 Exhaust lift (1.6:1 rocker ratio) 0.562 0.503 Lobe separation angle (deg) 110 112 Installed centerline (deg) 106 108 DYNO RESULTS 383 {{{Chevrolet}}} dyno test