Buick 300ci specs: 3.75 x 3.40 in (95.3 x 86.4 mm) bore and stroke, shared by all 3 versions. Displacement, compression and factory ratings, plus rod ratio.
| Displacement | 300 ci |
|---|---|
| Cylinders | 8 |
| Bore | 3.750" |
| Stroke | 3.400" |
| Compression | 9.0–11.0:1 |
| Advertised power | 210–250 hp |
| Years | 1964–1967 |
| Cylinder head data | 3 of 3 engines |
| Engine | Displacement | Bore × Stroke | CR | HP |
|---|---|---|---|---|
| Buick 300ci · 3.75" × 3.4" · 9:1 | 300 ci | 3.75" × 3.4" | 9:1 | 210 |
| Buick 300ci · 3.75" × 3.4" · 11:1 | 300 ci | 3.75" × 3.4" | 11:1 | 250 |
| Buick 300ci · 3.75" × 3.4" · 10.25:1 | 300 ci | 3.75" × 3.4" | 10.25:1 | 250 |
Compression spans 9:1 to 11:1, 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.