Bore, stroke, displacement and compression for all 8 Chevrolet 402ci engines, compared side by side. Plus rod ratio and head specs where published.
| Displacement | 402 ci |
|---|---|
| Cylinders | 8 |
| Bore | 4.065–4.125" |
| Stroke | 3.766–3.858" |
| Compression | 9.3–14.0:1 |
| Advertised power | 210–430 hp |
| Years | 1970–2023 |
| Cylinder head data | 2 of 8 engines |
| Engine | Displacement | Bore × Stroke | CR | HP |
|---|---|---|---|---|
| Chevrolet 402ci · 4.125" × 3.766" · 9.281:1 | 402 ci | 4.125" × 3.766" | 9.281:1 | 210–300 |
| Chevrolet 402ci (2023) · 430 hp | 402 ci | 4.065" × 3.858" | 14:1 | 430 |
| Chevrolet 402ci (1970) | 402 ci | 4.125" × 3.766" | — | 310 |
| L34 | 402 ci | 4.125" × 3.766" | — | 350 |
| L78 | 402 ci | 4.125" × 3.766" | — | 375 |
| LS3 | 402 ci | 4.125" × 3.766" | — | 330 |
| Z25 / L34 | 402 ci | 4.125" × 3.766" | — | 350 |
| Z25 / L78 | 402 ci | 4.125" × 3.766" | — | 375 |
Both bore and stroke vary across the family, so these are separate castings rather than variations on one block.
Compression spans 9.281:1 to 14:1, 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.