How much horsepower does a 400 small block have?

The horsepower of a 400 small-block Chevy engine varied significantly depending on the year of manufacture, the specific model, and any modifications made. There's no single answer. Factory ratings ranged from roughly 230 horsepower to well over 300 horsepower depending on the application (e.g., a car versus a truck, and options selected). A heavily modified 400 can produce far more than 300 hp.