Bore, stroke, displacement and compression for all 9 GMC Pontiac V8 engines, compared side by side. Plus rod ratio and head specs where published.
| Displacement | 287–455 ci |
|---|---|
| Cylinders | 8 |
| Bore | 3.750–4.120" |
| Stroke | 3.250–4.380" |
| Compression | 8.0–10.8:1 |
| Advertised power | 180–390 hp |
| Cylinder head data | 2 of 9 engines |
| Engine | Displacement | Bore × Stroke | CR | HP |
|---|---|---|---|---|
| 455 | 455 ci | 4.0598" × 4.3799" | 8.2:1 | 370 |
| 428 | 428 ci | 4.12" × 4" | 10.75:1 | 390 |
| 421 | 421 ci | 4.09375" × 4" | 10.75:1 | 370 |
| 400 | 400 ci | 4.12" × 3.75" | 10.75:1 | 360 |
| 389 | 389 ci | 4.0625" × 3.75" | 10.5:1 | 348 |
| 370 | 370 ci | 4.0598" × 3.6" | 10.5:1 | 300 |
| 347 | 347 ci | 4" × 3.5" | 10:1 | 270 |
| 316 | 316.6 ci | 3.9375" × 3.25" | 8.9:1 | 205 |
| 287 | 287 ci | 3.75" × 3.2799" | 8:1 | 180 |
Both bore and stroke vary across the family, so these are separate castings rather than variations on one block.
Compression spans 8:1 to 10.75:1, so fuel requirements differ meaningfully between members — worth checking before assuming parts interchange.
The family mixes oversquare and undersquare designs, so members behave quite differently despite sharing a name.
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.