6.7 liters is 408.9 cubic inches (6,700 cc) by straight math. Makers round, so the engines sold as 6.7 L measure from 406.2 to 410.7 cubic inches.
The most common: 410.5 ci (Mercury 410 (FE)); 409.1 ci (Chevrolet 409); 409.8 ci (Ford 406 (FE)); 406.2 ci (Ford 406); 410.7 ci (Ford 410); 408.3 ci (Ram 408 (Cummins ISB)).
| Engine | Codes | Years | Bore × stroke | Cubic inches | cc | Cylinders |
|---|---|---|---|---|---|---|
| Ford 410 | E-475 | 1958 | 4.203" × 3.700" | 410.7 | 6,730 | 8 |
| Chevrolet 409 | RPO 580, L31, L80, RPO 587 | 1961–1965 | 4.313" × 3.500" | 409.1 | 6,704 | 8 |
| Ford 406 (FE) | — | 1962–1963 | 4.150" × 3.787" | 409.8 | 6,715 | 8 |
| Mercury 410 (FE) | — | 1966–1967 | 4.051" × 3.980" | 410.5 | 6,726 | 8 |
| Ram 408 (Cummins ISB) | — | 2007–2026 | 4.213" × 4.882" | 408.3 | 6,690 | 6 (diesel) |
| Ford 406 | — | 2011–2026 | 3.900" × 4.250" | 406.2 | 6,656 | 8 (diesel) |
| Ford 408 | — | 2014–2015 | 4.213" × 4.882" | 408.3 | 6,690 | 6 (diesel) |
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.
408.9 cubic inches by straight conversion (1 liter = 61.024 cubic inches). Real 6.7 L engines measure 406.2 to 410.7 cubic inches; the table above lists each one.
6,700 cc by definition. The engines sold as 6.7 L range from 6,656 to 6,730 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.