Holley Ultra XP Circle Track carburetors are 38% lighter than the original HP, have fuel capacity that is 20% greater and 30 other new features! Holley Ultra XP Carburetors are specifically calibrated for Circle Track & offer new features such as anti-siphon valve in the main body; high capacity HP bowls which feature 20% more fuel capacity to eliminate starvation, integrated fuel shelf to minimize fuel aeration and internal baffling to control fuel slosh. Other features include all aluminum construction, fully tunable billet metering blocks, billet base plate, wedge floats, adjustable secondary linkage and knurled (hand adjustable) curb idle screws.