Bore, stroke, displacement and compression for all 14 Jeep AMC Straight-6 engines, compared side by side. Plus rod ratio and head specs where published.
| Displacement | 242–258 ci |
|---|---|
| Cylinders | 6 |
| Bore | 3.750–3.875" |
| Stroke | 3.410–3.900" |
| Compression | 8.8–9.2:1 |
| Advertised power | 110–195 hp |
| Years | 1971–2006 |
| Cylinder head data | 1 of 14 engines |
| Engine | Displacement | Bore × Stroke | CR | HP |
|---|---|---|---|---|
| 258 | 258 ci | 3.75" × 3.895" | 9.2:1 | 112 |
| 258 | 258 ci | 3.75" × 3.9" | 9.2:1 | 112 |
| AMC 258 1-bbl | 258 ci | 3.75" × 3.895" | — | — |
| AMC 258 2-bbl | 258 ci | 3.75" × 3.895" | — | — |
| AMC 258 | 258 ci | 3.75" × 3.895" | — | 110–150 |
| AMC Straight-6 (1972–1986) | 258 ci | 3.75" × 3.895" | — | 110–115 |
| 242 | 242 ci | 3.874" × 3.4134" | 8.8:1 | 190 |
| 4.0L HO | 242 ci | 3.8752" × 3.4098" | 8.8:1 | 190 |
| AMC Straight-6 · 3.875" × 3.410" · 9.2:1 | 242 ci | 3.8752" × 3.4098" | 9.2:1 | 177–190 |
| AMC 242 | 242 ci | 3.8752" × 3.4098" | — | 173–195 |
| AMC 242 MPI | 242 ci | 3.8752" × 3.4098" | — | 173–177 |
| AMC 242 H.O. | 242 ci | 3.8752" × 3.4098" | — | 190 |
| AMC 242 / Power-Tech Six | 242 ci | 3.8752" × 3.4098" | — | 180 |
| AMC 242 / 4.0L Power Tech I-6 | 242 ci | 3.8752" × 3.4098" | — | 181–190 |
Both bore and stroke vary across the family, so these are separate castings rather than variations on one block.
8 of 14 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.