What goes around comes around, especially now in the nostalgia- crazy '00s. While Barry Grant's conventional single-four-barrel Demon induction is thriving, it's sharing the fuel-mixing fame with three two-barrel carburetors that sit on a specially designed small-block intake manifold. This new setup keeps the high-performance Chevy crowd looking trendy, and adds horsepower and torque as well. We had to get a real good look at this new and improved piece of nostalgia.
The Six-Shooter Triple D induction features an aluminum intake manifold that has been engineered with race-inspired intake runners and a street-friendly plenum design. The manifold locates three two-barrel Demon carburetors and is equipped with a patent-pending thermostat housing. By design it minimizes leaks via a recessed well, accumulating seepage that would otherwise cause nasty stains on the manifold. All the carbs flow 250 cfm; the center one acts as the main unit and supplies off-idle air and fuel, and there's even a cold-start electric choke for die-hard winter enthusiasts.
Each carburetor carries a side-hung float bowl and takes direct orders from the throttle shaft of the primary carb. Simply put, the center toilet locates the throttle rod/cable and is connected to the outer carbs via a progressive throttle linkage. A billet aluminum fuel log feeds each carburetor's single inlet and is neatly mounted above the progressive throttle shafts. A banjo-style fitting accompanying each carburetor-to-fuel setup is designed to accept a tight compression fit using double O-rings around the inlet fuel tube. Once the fuel mixers and their accessories are fastened in place, a custom Rush air filter sits snugly on the carburetors.
When set-up correctly, the Six-Shooter Triple D induction is flat-out one of the best-looking and -performing induction systems period. During prototype testing, the Six-Shooter made outstanding power on a 350. At 5,800 rpm and 4,400 rpm, the Triple D made 13 more peak horse-power and 12 more lb-ft of torque than an industry-leading single-four-barrel manifold design. With such impressive numbers coming from a nostalgic design, we just had to test one of these triple-carb deals for ourselves.
Since the very beginning of all this hop-up business, the triple-carburetor induction design has maintained a solid rep for its outstanding ability to offer crisp throttle response while making impressive low-speed torque as well as horsepower. With power on the brain, we decided to see how much grunt a stroked small-block could make with the trips. Our candidate was a Smeding Performance 383ci short-block featuring a 3.75-inch stroke GM steel crankshaft, 5.7-inch I-beam connecting rods with ARP bolts, and hypereutectic 4.030-inch overbore pistons. When sealed with a 5-quart oil pan and two-piece Edelbrock timing cover, it was ready for the induction plan.
With a stroker motor there is usually plenty of torque to go around, so we decided to push the envelope and screw some 215cc intake runner Dart Iron Eagle cylinder heads over the Fel-Pro sealed hypereutectic pistons. COMP Cams set us up with a complete hydraulic-roller valvetrain featuring 0.510/0.540-inch intake and exhaust lifts with 230/244 degrees of duration at 0.050-inch-lift measuring points. It was ground on a 112-LSA and offered power-brake-capable vacuum at an 850-rpm idle and a 6,000-rpm wing. We slid hydraulic roller lifters and one-piece Magnum pushrods on top of the bumpstick.
The Dart 215cc heads come with hefty valvesprings, 3/8-inch rocker studs, and one-piece pushrods. The pushrods will most likely have to be checked for proper length as well. COMP's screw-out adjustable pushrod makes this process as simple as possible. Once we installed the proper length pushrods for our application, the COMP Cams hudraulic roller rockers had no problem clearing the valvespring retainers. We adjusted the valves and attached cast aluminum COMP Cams valve covers.
We set the Six-Shooter Triple D induction in place. The Dart 215cc heads call for a Fel-Pro race intake gasket (PN: 1206), but when used with the Triple D, the Fel-Pro PN 1205 looked like a better way to match up the water passages and intake runner openings. We secured the manifold with ARP intake bolts and adjusted the throttle linkage.
MSD Ignition sent a Pro-Billet housing featuring a standard cap distributor. When clearance between the rear carburetor bowl and distributor cap becomes an issue, the standard cap usually supplies enough room. We finished the system off with custom-fit 8.5mm spark plug wires, a wire-crimping tool, Pro-Clamp wire separators, and heat shield boots for protection from the 1 5/8-inch Hedman Headers surrounding the tapered-seat 1/2-inch-reach Champion spark plugs.
Testing 1, 2, 3
While BG found big gains in peak power numbers, we decided to review the average power numbers between 2,500 and 6,000 rpm. Our first series of tests was performed without the Rush air filter. We altered the fuel curve to read a near-perfect 12.2:1 air-fuel ratio, while total spark timing came in at 38 degrees. It was combined with a slow advance curve to muzzle detonation in the lower rpm ranges. After reaching ideal engine-operating temps, our stroked small-block delivered a peak of 439 lb-ft of torque at 4,200 rpm and 399 hp at 5,800 rpm. The average numbers posted an even more amazing 410 lb-ft of torque and 330 hp across the board. We wanted to see the effect, if any, of the Rush air filter on the Triple D.
The custom-made Rush air filter assembly fits tightly over the three carburetors to yield hood clearance without restricting power, regardless of crankshaft speed. All other factors remained constant. Surprisingly, the air filter barely disturbed the airflow entering the carburetors and no air/fuel tuning was required. The power numbers did drop slightly, but comparing them to the previous ones reveals that such a minimal decrease would not be measurable by on-track testing. The peak numbers came in at 437 lb-ft of torque at 4,200 rpm and 397 hp at 5,400 rpm. Average numbers with the Rush filter combination were 407 lb-ft of torque and 330 hp--3 lb-ft less, on average, while posting identical average horse-power readings.
We couldn't resist putting the Triple D up against one of the industry's leading four-barrel manifolds. We swapped on a dual-plane plenum intake manifold and used a 750-cfm Speed Demon, but all the other variables were unchanged. After a few pulls, the industry leader posted less torque but more top-end horsepower. At 4,300 rpm we recorded 431 lb-ft of torque and 415 hp at 5,700 rpm. Average numbers came in at 405 lb-ft and 328 hp. While these numbers look weird, take a look at the dyno curves. This particular intake was weak on torque across the board; at approximately 4,600 rpm and below, its horsepower numbers were down as well. Above 4,600 rpm, its peak horsepower numbers climbed above the Six-Shooter's, but only slightly, causing the overall horsepower curve to fall shy of the Six-Shooter's by 2 hp on average.