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Genesis G8BA specs: 5.0L (307 ci) 8-cylinder, 96 x 87 mm (3.7795 x 3.4252 in) bore and stroke, 11.5:1 compression. Rated 420 hp. Rod ratio and piston speed.
The Genesis G8BA is oversquare — the 3.7795" bore exceeds the 3.4252" stroke by 10.3% — a layout that favors airflow and RPM over leverage at the crank. The 3.4252" stroke puts mean piston speed at 4,000 ft/min around 7,000 RPM, which is where a production bottom end is generally considered at its limit. Each of the 8 cylinders displaces 38.4 ci (629 cc).
11.5:1 on aluminum heads is high for a production gasoline engine; running a ratio like that on pump fuel depends on chamber design and fuel delivery rather than the number alone.
Factory fitments include the Genesis G80, Genesis G90.
| Displacement | 307 ci / 5 L |
|---|---|
| Bore | 3.7795" |
| Stroke | 3.4252" |
| Cylinders | 8 |
| Compression ratio | 11.5:1 |
| Bore/stroke ratio | 1.103 |
| Block material | aluminum |
|---|---|
| Head material | aluminum |
| Valvetrain | DOHC |
| Fuel type | gas |
| Advertised HP | 420 hp |
| Bore/stroke character | 1.103 — oversquare — bore exceeds stroke, which favours higher RPM and larger valves |
|---|---|
| Mean piston speed at 6,000 RPM | 3,425 ft/min — conservative for a street engine |
| Displacement per cylinder | 38.4 ci |
| Static compression | 11.5:1 — high enough that pump premium or better is normally required |
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