He began his career at Piaggio, makers of the Vespa scooter, but quickly moved up to larger engines. He worked at Isotta-Fraschini before World War II, and then joined Reggiane to design aircraft engines.
Lampredi's fame brought him to Ferrari in 1946 where he designed a large 4.5 L V12 (the "Lampredi engine") which first saw use in 1950's 257S. Lampredi returned to Isotta-Fraschini in March 1947 but returned to Ferrari at the beginning of 1948. Lampredi's engines were used as large naturally-aspirated alternatives to the diminutive Gioacchino Colombo-designed V12s used in most Ferrari cars until that time. Especially after the failure of Colombo's supercharged engine in Formula 1, Lampredi's design began to find favor in the company. Lampredi oversaw Ferrari's racing effort during its early success in 1952 and 1953.
Lampredi's work at Ferrari ended permanently in 1955 when Ferrari bought Lancia's racing team and famed engine designer Vittorio Jano, formerly of Alfa Romeo. Though Lampredi's engine designs lived on in Ferrari road cars, Jano's V6 and V8 engines quickly replaced Lampredi's large V12s for racing use.
After Ferrari, Lampredi went to Fiat, where he oversaw that company's engine design efforts until 1977. It was at Fiat where he designed the Fiat Twin-Cam and SOHC engines, which provided motive-force for most Fiat automobiles for over 32 years. He was also made manager of Fiat's Abarth factory racing group from 1973 through 1982.