I must be slipping. I hate folks who post a question and then don't answer it.
The first car to have 1 horsepower per cubic inch was the 1956 Chrysler 300B with the optional high compression heads giving 354 hp from 354 inches.
The first car to have it as standard was the 1957 DeSoto Adventurer. It had 345 hp out of a 345 engine. By the way, both engines were Hemis.
Honk if you love Jesus.
Text if you want to meet him.
What was the first production car to have 100 HP / liter?
Definitely the Hummer. Pretentious, faux-military gas guzzler. Screams 'My SUV* is bigger than yours!
*can substitute a certain body part here for the same effect