PROFORM's new Aluminum Street Series Upgrade Carburetor is hand assembled in the U.S. Based on the wildly successful Billet Aluminum Street Series carburetors the new PROFORM Upgrade carburetors are constructed of lightweight aluminum including changeable idle air bleeds for easy non-permanent calibration changes if needed. Keep your drills in your tool box; fine tuning is accomplished by simply changing air bleeds not opening calibration restrictions with a drill bit. Each street carburetor features metering blocks with a street performance calibration that's ready to roll right out of the box, and developed for today's high performance engines. Four corner idle on mechanical secondary carburetors to help fine tune the idle with aggressive camshaft profiles. Changeable idle feed restrictions further expand the idle adjustment capabilities. Conventional service and tuning components are available in most performance retail outlets. The package is completed with high quality, light weight die-cast aluminum fuel bowls with fuel level windows for quick visual reference. Float level changes do not require removal of a sight plug with the risk of fuel spilling all over the top of your engine. Bowls come equipped with 3/8in inverted flare fuel inlet fittings and will accept all conventional dual feed fuel lines compatible with Holley four barrel carburetors. Like all PROFORM carburetors, service parts are readily available however, should you not find PROFORM service parts, our carburetors are compatible with any modular carburetor service parts available at your local parts store or favorite retail outlet.