The size of a carburetor is an important consideration when selecting one for an engine. The optimal carburetor size depends on various factors, including the engine's displacement, intended use, and modifications.
For a typical stock or mildly modified 350 cubic inch (5.7-liter) engine, a 650 CFM (cubic feet per minute) carburetor is generally considered to be on the larger side. A smaller carburetor, such as a 600 CFM or even 500 CFM, may provide better throttle response and fuel efficiency in most cases.
Additionally, if the engine is intended for high-performance or racing applications, where increased airflow is essential, a 650 CFM carburetor could be suitable.
Ultimately, the best carburetor size depends on the specific combination of components and the desired performance characteristics. It is always recommended to consult with experienced engine builders or tuners who can provide personalized recommendations based on your engine's specifications and goals.