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Buick 400ci (1969) specs: 400 ci 8-cylinder, 4.04 x 3.90 in (102.6 x 99.1 mm) bore and stroke, 10.25:1 compression. Rated 345 hp, 1969.
The Buick 400ci (1969) is close to square: 4.04" bore against 3.9" stroke, within 3.6%, which splits the difference between a high-revving layout and a torque layout. The 3.9" stroke puts mean piston speed at 4,000 ft/min around 6,150 RPM, which is where a production bottom end is generally considered at its limit. Each of the 8 cylinders displaces 50.0 ci (819 cc).
10.25:1 is in the range that usually runs on pump premium.
It is one of 4 engines in the Buick 400ci family, all of them 400 ci — the differences between them are in compression, heads and rating, not displacement.
| Displacement | 400 ci |
|---|---|
| Bore | 4.04" |
| Stroke | 3.9" |
| Cylinders | 8 |
| Configuration | V8 |
| Compression ratio | 10.25:1 * |
| Bore/stroke ratio | 1.036 |
* Compression ratio from a single source; not yet cross-verified.
| Fuel type | gas |
|---|---|
| Firing order | 1-8-4-3-6-5-7-2 |
| Advertised HP | 345 hp |
| Years | 1969 |
| Bore/stroke character | 1.036 — square — bore and stroke are within 5%, a balanced compromise |
|---|---|
| Mean piston speed at 6,000 RPM | 3,900 ft/min — in the range typical of performance street engines |
| Displacement per cylinder | 50.0 ci |
| Static compression | 10.25:1 — in the range that usually runs on pump premium |
Each link opens the calculator with this engine's specs already filled in.
1 factory vehicle, 1969. Each year opens that model's engine table.