GMC Vortec 4200 (4.2L I6) specs: 3.661 x 4.016 in (93 x 102 mm) bore and stroke. Displacement, compression and factory ratings, plus rod ratio.
| Displacement | 256 ci |
|---|---|
| Cylinders | 6 |
| Bore | 3.661" |
| Stroke | 4.016" |
| Compression | 10.0:1 |
| Advertised power | 275–291 hp |
| Engine | Displacement | Bore × Stroke | CR | HP |
|---|---|---|---|---|
| LL8 | 256 ci | 3.6614" × 4.0157" | 10:1 | 275–291 |
This family is represented by a single engine in the database: 256 ci, 6 cylinders, a 3.6614" × 4.0157" bore and stroke.
All are undersquare — stroke larger than bore, favouring torque low in the range.
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.