Holley 34-13SA Secondary Metering Block Conversion Kit - Shiny Aluminum4160 to 4150 Conversion Kit for 0 3310SA and 0 80508SA Part Number: 34 13SA Easily convert your 0 3310SA or 0 80508SA 750 CFM carburetor to a model 4150 by adding a secondary metering block. The addition of a secondary metering block will allow you to fine tune your carburetor by utilizing replaceable main jets versus the fixed orifices found in a metering plate. Features and Benefits No Provision For Power Valve Alows The Use of Metering Jets