Carbulator

Carbulator is a fun and easy to use iPhone application that calculates carburetor CFM, enabling the user to determine the proper size carburetor that an engine needs for optimal performance and efficiency. The user can change values for CID, RPM and VE and change outcomes. Carbulator is a great reference tool for everyone from the casual hobbyist to the professional counterman and everyone in between.
Get it while it's free, and remember size matters!