In this age when the trend is to fuel inject all the things, it’s nice to see a new company like Fuel Systems Technology (FST) making performance carburetors. When properly set up, a carburetor can make as much—if not more—power, and some folks just prefer tuning with a screwdriver than a computer.
Summit Racing carries FST’s Billet X-treme and Billet X-treme Pro series carburetors. Both have these features:
• CNC-machined 4150-style billet aluminum main body
• Billet aluminum metering blocks with five removable emulsion bleeds for excellent tunability
• Billet baseplate drilled for 4150 and 4500 mounting flanges
• Stainless steel throttle shafts and Teflon-sealed butterflies perfect for turbo/supercharged engines
• Four-corner idle adjustment for fine tuning and better fuel distribution
• 30cc accelerator pump
• Quick-change jets and idle circuit air bleeds
• Can use 4150-type jets, air bleeds, and other parts made by other carburetor manufacturers
The Billet X-treme carburetors also feature FST’s Viper fuel bowls. The billet aluminum bowls have center-hung nitrophyl floats, internal baffling to prevent fuel slosh, dual fuel sight windows, and dual drain plugs that let you replace the jets without removing the bowls. The Viper bowls also have three inlet fittings—a center-mount -8AN O-ring inlet and two traditional 7/8-20 side inlets—to make fuel system connections more convenient.
Another cool feature is the bolt-on bracket to mount a throttle position sensor (TPS) switch. This allows you to hook up an electronic overdrive transmission or a data logger that requires a TPS signal.
The primary difference between the Billet X-treme and X-treme Pro carburetors is the number of circuits in the metering blocks. The standard X-tremes have two-circuit blocks, the Pros have three-circuit blocks. That third circuit allows part-throttle tuning between idle and when the main metering circuit begins to flow fuel. This OnAllCylinders article explains two- vs. three-circuit metering more fully.
FST Billet X-treme carburetors are available in 650 and 750 cfm ratings with vacuum or mechanical secondaries. The X-treme Pro carburetors are available in 850, 950, and 1,050 cfm ratings with mechanical secondaries only.
SEE FST BILLET X-TREME SERIES CARBURETORS AT SUMMIT RACING