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Plymouth 400 4-bbl Lean Burn specs: 400 ci (6.6L) 8-cylinder, 4.342 x 3.375 in (110.3 x 85.7 mm) bore and stroke. Rated 190 hp, 1977–1978.
The Plymouth 400 4-bbl Lean Burn is oversquare — the 4.342" bore exceeds the 3.375" stroke by 28.7% — a layout that favors airflow and RPM over leverage at the crank. The 3.375" stroke does not reach 4,000 ft/min of mean piston speed until about 7,100 RPM, so piston speed is not what limits this engine's revs — valvetrain and breathing are. Each of the 8 cylinders displaces 50.0 ci (819 cc).
It is one of 27 engines in the B family, the largest at 400 ci. 2 factory variants share these dimensions, rated at 190 hp across 1977–1978.
| Displacement | 400 ci / 6.6 L |
|---|---|
| Bore | 4.342" |
| Stroke | 3.375" |
| Cylinders | 8 |
| Configuration | V8 |
| Bore/stroke ratio | 1.287 |
| Valvetrain | OHV |
|---|---|
| Fuel type | gas |
| Advertised HP | 190 hp |
| Years | 1977–1978 |
| Bore/stroke character | 1.287 — oversquare — bore exceeds stroke, which favours higher RPM and larger valves |
|---|---|
| Mean piston speed at 6,000 RPM | 3,375 ft/min — conservative for a street engine |
| Displacement per cylinder | 50.0 ci |
Each link opens the calculator with this engine's specs already filled in.
These records share identical bore, stroke, displacement and compression. They differ by model year and factory power rating.
| Year | Advertised HP | Code |
|---|---|---|
| 1977 | 190 hp | 400 4-bbl Lean Burn |
| 1978 | 190 hp | 400 4-bbl Lean Burn |