6.8 liters is 415.0 cubic inches (6,800 cc) by straight math. Makers round, so the engines sold as 6.8 L measure from 412.0 to 417.0 cubic inches.
The most common: 413.2 ci (Plymouth 413 (RB)); 412.6 ci (Ford 415 (Modular)); 417.0 ci (Mercedes-Benz 417); 412.0 ci (Ford 412 (Godzilla)).
| Engine | Codes | Years | Bore × stroke | Cubic inches | cc | Cylinders |
|---|---|---|---|---|---|---|
| Plymouth 413 (RB) | RB 413 | 1959–1965 | 4.188" × 3.750" | 413.2 | 6,771 | 8 |
| Mercedes-Benz 417 | M100 | 1978–1979 | 4.213" × 3.740" | 417.0 | 6,834 | 8 |
| Ford 415 (Modular) | — | 1997–2018 | 3.551" × 4.165" | 412.6 | 6,761 | 10 |
| Ford 412 (Godzilla) | — | 2023–2026 | 4.221" × 3.681" | 412.0 | 6,751 | 8 |
Cubic inches and cc are worked out from each engine's bore and stroke. Years are the model years of the factory cars on this site that list the engine.
Start with the engine code: on 1981-and-later cars and trucks it is a character of the VIN (the 8th on most American makes), and most blocks carry a code stamp. Each engine's page lists its codes and the cars it came in. See the VIN engine code lists by make.
415.0 cubic inches by straight conversion (1 liter = 61.024 cubic inches). Real 6.8 L engines measure 412.0 to 417.0 cubic inches; the table above lists each one.
6,800 cc by definition. The engines sold as 6.8 L range from 6,751 to 6,834 cc.
Makers name engines by rounded sizes. The real size comes from bore × bore × stroke × 0.7854 × cylinders, so two engines sold as the same size are often a few cubic inches apart.