Bore, stroke, displacement and compression for all 7 GMC Oldsmobile V8 engines, compared side by side. Plus rod ratio and head specs where published.
| Displacement | 307–425 ci |
|---|---|
| Cylinders | 8 |
| Bore | 3.799–4.126" |
| Stroke | 3.382–4.000" |
| Compression | 8.0–10.5:1 |
| Advertised power | 140–370 hp |
| Years | 1996–1998 |
| Cylinder head data | 1 of 7 engines |
| Engine | Displacement | Bore × Stroke | CR | HP |
|---|---|---|---|---|
| 425 | 425 ci | 4.126" × 4" | 10.25:1 | 370 |
| 403 | 403 ci | 4.126" × 3.752" | 8:1 | 185 |
| 400 | 400 ci | 4" × 3.975" | 10.5:1 | 345 |
| 350 | 350 ci | 4" × 3.5" | 9:1 | 310 |
| L31 | 350 ci | 4" × 3.5" | — | 255 |
| 330 | 330 ci | 3.938" × 3.385" | 10.25:1 | 260 |
| 307 | 307 ci | 3.7992" × 3.3819" | 8:1 | 140 |
Both bore and stroke vary across the family, so these are separate castings rather than variations on one block.
Compression spans 8:1 to 10.5:1, so fuel requirements differ meaningfully between members — worth checking before assuming parts interchange.
5 of 7 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.