GMC 401ci specs: 4.065 x 3.858 in (103.3 x 98 mm) bore and stroke. Displacement, compression and factory ratings for each, plus rod ratio and piston speed.
| Displacement | 400.6 ci |
|---|---|
| Cylinders | 8 |
| Bore | 4.065" |
| Stroke | 3.858" |
| Years | 2021–2026 |
| Engine | Displacement | Bore × Stroke | CR | HP |
|---|---|---|---|---|
| L8T | 400.6 ci | 4.065" × 3.8583" | — | — |
This family is represented by a single engine in the database: 400.6 ci, 8 cylinders, a 4.065" × 3.8583" bore and stroke.
All are oversquare — bore larger than stroke, which favours revs over low-end torque.
Each engine page carries rod ratio, mean piston speed, bore/stroke character and cylinder head specs where published, and links into the calculators with its dimensions already filled in.