Bore, stroke, displacement and compression for all 3 Buick 400ci engines, compared side by side. Plus rod ratio and head specs where published.
| Displacement | 400 ci |
|---|---|
| Cylinders | 8 |
| Bore | 4.040–4.188" |
| Stroke | 3.640–3.900" |
| Compression | 10.3–11.0:1 |
| Advertised power | 325–350 hp |
| Years | 1965–1969 |
| Cylinder head data | 3 of 3 engines |
| Engine | Displacement | Bore × Stroke | CR | HP |
|---|---|---|---|---|
| Buick 400ci · 4.188" × 3.64" · 10.25:1 | 400 ci | 4.188" × 3.64" | 10.25:1 | 325 |
| Buick 400ci · 4.188" × 3.64" · 11:1 | 400 ci | 4.188" × 3.64" | 11:1 | 332 |
| Buick 400ci · 4.04" × 3.9" · 10.25:1 | 400 ci | 4.04" × 3.9" | 10.25:1 | 340–350 |
Both bore and stroke vary across the family, so these are separate castings rather than variations on one block.
2 of 3 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.