The modular-style four-barrel carburetor introduced decades ago has eclipsed all other carb configurations, dominating the high performance carburetor market. Racers loved the easy tuning of the main circuit via a simple jet change, while the manufacturer could offer a broad range of carb capacities by changing the main body and baseplate. The interchangeability of parts and simple, functional design has made the 4150 configuration the small-block Chevy of carburetors.
Just like with the small-block Chevy, other manufacturers have pushed the design features and performance capabilities to levels far exceeding what the original designer may have imagined. Quick Fuel Technology (QFT) is a company that specializes in building the hot rods of carburetors. Those old Holley carbs of the 1960s did one thing well, and that was wide-open-throttle performance in a straight line. The die-cast zinc construction weighed a ton and was subject to corrosion. The flash zinc dichromate finish wore to a dull gray straight out of the box, and other than jets, critical metering orifices required drilling to effectuate a crude tuning change.
Like all Quick Fuel Technology carbs, the new BDQ-Series features weight-saving aluminum construction. The new Black Diamond coating (right) is not just for show, but is highly temperature, fuel, and corrosion resistant, while reducing carb temperature by approximately 6 percent.
Much like aftermarket engine blocks and cylinder heads have done for the small-block Chevy, QFT took that basic modular carburetor configuration and packed in a tremendous level of performance and convenience. We tapped into the expertise at QFT and selected a 950-cfm BDQ-950 for a very high-powered Ford street/road racing engine project. This series of carb is also available in 650-, 750-, and 850-cfm capacities, with 1,000- and 1,050-cfm versions offered by QFT's custom shop. Our BDQ-950 had the familiar 4150 layout, making it a direct bolt-in for any standard 4150-flange performance intake manifold. The tuning parts and gaskets are the same pieces found in our stash of Holley parts, and even our double-pumper fuel line kit will interchange. That stuff is all standardized, but the features set the QFT apart, especially at a price point of just over the $800 mark.
Engineered Improvements
The sinister black finish is the first thing you'll notice when looking at the BDQ carb, and it's not just for looks. The high-temperature Black Diamond coating is highly chemical and fuel resistant, a critical advantage when considering the corrosive nature of today's fuel formulations. The kicker is this coating is also designed to reduce heat, with testing at Quick Fuel showing a 6 percent temperature advantage. Lower temperatures reduce the likelihood of heat soak, which can make driveability a challenge. Pick the carb up and you'll immediately feel the reduced heft, a drop of about 4 pounds owing to the carb's all-aluminum construction. You'll spy the big shatterproof sight glass windows in the bowl. These are clearly going to be appreciated when setting the floats, compared to pulling the old-fashioned bowl plugs and dribbling fuel all over the engine.
For road racing, our carb was equipped with wedge-shaped floats from the QFT custom shop. This arrangement clears the jet extensions while minimizing needle and seat disturbances from fuel sloshing under high cornering forces.
Look closer and notice the nicely shaped streamlined venturi entry, responsive downleg boosters, replaceable idle and high-speed air bleeds, and billet metering blocks and baseplate. A sharp eye will pick out the wider accelerator pump cams operating the dual 30cc accelerator pump, increasing surface area for reduced wear. You might also note there is something different about the linkage to the secondaries. If you want your airflow to come on "right now," Quick Fuel has you covered. QFT's unique linkage arrangement offers tunable secondary opening rates. The standard progression starts secondary opening at 60 percent primary opening, while a link change will time the secondary to start at just 40 percent primary engagement, or a third option for synchronized 1:1 opening.
Exploring further with a look inside the unit finds replaceable idle feed restrictions, and power valve channel restrictions, both critical to fine-tuning such a large carburetor in a demanding street/race application. You'll also see notched floats and jet extensions in the secondary to reduce the possibility of fuel starvation under acceleration. Our carb goes one step further, being prepped by the QFT custom shop with their double-edge wedge-shaped float. This design concentrates the buoyancy at the center of the float, ideal for road racing where fuel sloshing to the sides can disrupt fuel delivery.
A selection of interchangeable secondary links change the timing of the secondary tip-in from a standard 60 percent primary opening, to a quicker 40 percent, or even a 1:1 configuration. The quicker timing may better match some drivers’ styles on the track.
With its advanced performance features, this QFT is as far ahead of the original 4150 carb as a custom race engine is compared to the stock 350 in your pickup. This BDQ is engineered from the start as a hot rodded carb. We have had plenty of experience with QFT's carb offerings, and recognize that the build quality and workmanship is second to none. The quality and engineering have us looking forward to putting this unit to task on the street and track.
