Bore, stroke, displacement and compression for all 24 Mercury Windsor engines, compared side by side. Plus rod ratio and head specs where published.
| Displacement | 221–351 ci |
|---|---|
| Cylinders | 8 |
| Bore | 3.500–4.000" |
| Stroke | 2.870–3.500" |
| Compression | 8.2–10.7:1 |
| Advertised power | 115–300 hp |
| Years | 1962–1993 |
| Cylinder head data | 1 of 24 engines |
| Engine | Displacement | Bore × Stroke | CR | HP |
|---|---|---|---|---|
| 351W | 351 ci | 4" × 3.5" | 9.5:1 | 250 |
| 351W EFI | 351 ci | 4" × 3.5" | 8.8:1 | 210 |
| 351W | 351 ci | 4" × 3.5" | 10.7:1 | 290 |
| 351W EFI | 351 ci | 4" × 3.5" | — | — |
| Windsor (1969–1979) | 351 ci | 4" × 3.5" | — | 135–250 |
| M-code | 351 ci | 4" × 3.5" | — | 285–300 |
| Q-code | 351 ci | 4" × 3.5" | — | 255–280 |
| Q-code + CJ Performance Group | 351 ci | 4" × 3.5" | — | 266 |
| Windsor 351 | 351 ci | 4" × 3.5" | — | 138–145 |
| Windsor · 4.000" × 3.000" · 9:1 | 302 ci | 4" × 3" | 9:1 | 150–225 |
| 302 | 302 ci | 4" × 3" | 10:1 | 230 |
| Windsor (1968–1993) | 302 ci | 4" × 3" | — | 130–290 |
| J-code | 302 ci | 4" × 3" | — | 230 |
| Windsor 5.0 | 302 ci | 4" × 3" | — | 129–160 |
| 289 | 289 ci | 4" × 2.8701" | 9.3:1 | 200 |
| 289 HiPo | 289 ci | 4" × 2.8701" | 10.5:1 | 271 |
| C-code | 289 ci | 4" × 2.8701" | — | 195–200 |
| Windsor (1967) | 289 ci | 4" × 2.8701" | — | 225 |
| 260 | 260 ci | 3.7992" × 2.8701" | 8.8:1 | 164 |
| 255 | 255 ci | 3.6811" × 3" | 8.2:1 | 115–120 |
| Windsor (1980–1982) | 255 ci | 3.6811" × 3" | — | 115–122 |
| Windsor 4.2 | 255 ci | 3.6811" × 3" | — | 120–122 |
| 221 | 221 ci | 3.5" × 2.8701" | 8.7:1 | 145 |
| L-code | 221 ci | 3.5" × 2.8701" | — | 145 |
Both bore and stroke vary across the family, so these are separate castings rather than variations on one block.
Compression spans 8.2:1 to 10.7:1, so fuel requirements differ meaningfully between members — worth checking before assuming parts interchange.
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.