What was the engine displacement of the 1970 Ford Mustang Boss 429?

What was the engine displacement of the 1970 Ford Mustang Boss 429? It was 429 cubic inches. The number identifies the engine’s nominal displacement and is the source of the model’s name.

The Boss 429 was created primarily to help Ford homologate a race-oriented V8 for NASCAR. Ford installed the engine in a limited run of Mustang fastbacks so the competition engine could meet rules requiring production-based cars. The engine used a large Ford 385-series block, aluminum cylinder heads, a semi-hemispherical combustion-chamber design, and heavy-duty internal components.

The Boss 429 was offered for the 1969 and 1970 model years, not just 1970. Although its advertised output was relatively modest by later standards, the engine’s design was aimed at sustained high-rpm racing rather than simply showroom horsepower figures. Its physical size also required extensive front-structure changes by Kar Kraft before the engine could fit in the Mustang.

Do not confuse it with the smaller Boss 302, a 302-cubic-inch small-block Mustang developed for Trans-Am competition. Ford produced 499 Boss 429s for 1970, following 860 examples in 1969.