Fuel Line Size
"When it comes to selecting the correct size of feed and return lines, there is no generic chart to guide users. Often, the application or the style of fuel pump will determine fuel-line size. To ensure adequate volume and reduce the risk of cavitation, feed the pump with a hose one size larger than that being used for the main supply line. Return lines on EFI applications are generally smaller than those used on carbureted motors because of the higher working pressures involved. Typically, an EFI flow-through pump system supporting up to 750 hp will have an AN-10 line between the tank and pump, an AN-8 feed line, and an AN-6 return line. On an equivalent carbureted application of similar horsepower, the feed-line sizes remain the same, but the return-line size should be increased to AN-10. On carbureted applications, the return line can discharge its fuel into the top of the tank or cell, whereas fuel-injected applications should discharge their return fuel into an internal pipe located in the rear of the tank with its outlet near the bottom. This prevents fuel aeration. The bore size of the internal pipe in the tank or cell must be equivalent to that of the return line that feeds it. Both carbureted and EFI systems should employ a filtered AN-8 vent hose from the tank to the atmosphere."
Porosity
"Eliminating porosity is very important in the proper function of a carburetor. Before the evolution of billet metering blocks, hoards of frustrated racers complained about poor-performing engines that mysteriously lost 10-15 hp. Then, by simply changing a metering block, the problem vanished. Though the porosity was hidden, fuel-metering passages were joined internally, causing meager performance and poor idle and drivability. Ten years ago, when the first Demon carbs were designed, measures were taken during the casting process to prevent core shift between the upper and lower halves of the carburetor's main body. Experimenting with freer-flowing air entries and repeatable concentric venturi gave the new carburetor a performance advantage. In addition to using billet components, new high-density casting techniques significantly reduce porosity compared to conventional casting methods."
Materials
The adage "you get what you pay for" certainly applies to carburetors, and just because components look the same doesn't mean they are the same. The most commonly used materials in BG carbs are billet aluminum, cast aluminum, cast zinc, and brass, and the company doesn't compromise quality to reduce production costs. "So far, we've maintained loyalty to U.S.-made raw materials, as none of our castings are produced offshore," explains BG. "Offshore products may prove satisfactory in the long run, but we're sticking with domestic materials in the meantime. Last year, we observed cast-zinc carburetor components that had suffered an odd powdery deterioration, and we concluded that they were cast overseas. Our foundry owners check each load of raw materials and reject those that do not meet their standards. With the recent upsurge in demand for scrap metals, who knows what happens abroad?"
Automation
Watching robots whittle engine components out of raw metal stock is great entertainment, but the real benefit of automated manufacturing is improved quality. CNC machines and digital probes improve consistency far beyond what's possible with manual labor. "Twelve or 15 years ago, our industry had a defining moment," explains BG. "Suddenly, complex product shapes were repeatable, tolerances were tightened, quality assurance improved, profiles that were previously difficult to achieve could be produced effortlessly, and production increased as the new machines ran night and day. All this resulted in higher quality at a lower price."