What’s the best way for a racer using a carburetor to optimize engine performance?

Testing for maximum 60 foot performance should be done first.  Jetting, accelerator pump, transition circuits, float level, and/or fuel pressure adjustments should be done for this first phase of drag racing performance.  After carburetor adjustments are done to optimize the 60 foot time, then further adjustments can be done for mid-range and high-end performance.

Specific to air/fuel ratio tuning, adjustments for air density changes are effective once a carburetor combination is set up.  Those include the appropriate jetting and other adjustments to fuel flow.

Changes to carburetor venturi size or design to optimize engine performance are more involved and can dramatically affect a prior optimum combination.  Error’ing on the small venturi size is less risky than error’ing on the large venturi size.  Converting from progressive to straight linkage can be troublesome, especially for racecars with manual transmissions or tight converters.  Converting from vacuum to mechanical secondary linkage can also be troublesome if appropriate other features such as double pumper provisions are not included or the engine is lugged.

For a new combination, it would not be a bad idea to start out with the most conservative ‘slave’ carburetor setup such as a small vacuum secondary unit or an older unit from a previous running combination to get through the infant mortality of engine break-in and chassis adjustments.  Then, after initial sorting, the killer ‘master’ carburetor could be installed to set up for max performance.