Bore, stroke, displacement and compression for all 3 GMC Chevy Straight-6 (235/261) engines, compared side by side. Free spec reference.
| Displacement | 235–261 ci |
|---|---|
| Cylinders | 6 |
| Bore | 3.875" |
| Stroke | 3.313–3.688" |
| Compression | 7.5–8.0:1 |
| Advertised power | 105–150 hp |
| Years | 1962 |
| Engine | Displacement | Bore × Stroke | CR | HP |
|---|---|---|---|---|
| 261 | 261 ci | 3.8752" × 3.6882" | 8:1 | 140 |
| Chevy Straight-6 (235/261) (1962) | 261 ci | 3.8752" × 3.6882" | — | 150 |
| 235 | 235 ci | 3.8752" × 3.3126" | 7.5:1 | 105 |
Every engine here shares a 3.8752" bore; displacement varies by stroke alone, which is the signature of a family built on one block with different cranks.
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.