Buick 307ci specs: 3.80 x 3.385 in (96.5 x 86 mm) bore and stroke, shared by all 2 versions. Displacement, compression and factory ratings, plus rod ratio.
| Displacement | 307 ci |
|---|---|
| Cylinders | 8 |
| Bore | 3.800" |
| Stroke | 3.385" |
| Compression | 9.2–9.6:1 |
| Advertised power | 140–145 hp |
| Years | 1985–1988 |
| Cylinder head data | 1 of 2 engines |
| Engine | Displacement | Bore × Stroke | CR | HP |
|---|---|---|---|---|
| Buick 307ci · 3.800" × 3.385" · 9.611:1 | 307 ci | 3.8" × 3.385" | 9.611:1 | 140–145 |
| 1988 307 140HP | 307 ci | 3.8" × 3.385" | 9.241:1 | 140 |
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.