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Mercury 3.8L specs: 232 ci (3.8L) 6-cylinder, 3.811 x 3.39 in (96.8 x 86.1 mm) bore and stroke, 9:1 compression. Rated 155 hp. Rod ratio and piston speed.
The Mercury 3.8L is oversquare — the 3.811" bore exceeds the 3.3898" stroke by 12.4% — a layout that favors airflow and RPM over leverage at the crank. The 3.3898" 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 6 cylinders displaces 38.7 ci (634 cc).
9:1 on iron heads is low by modern standards and generally happy on regular pump fuel.
It is one of 7 engines in the Essex family, all of them 232 ci — the differences between them are in compression, heads and rating, not displacement. Factory fitments include the Mercury Sable, Mercury Cougar.
| Displacement | 232 ci / 3.8 L |
|---|---|
| Bore | 3.811" |
| Stroke | 3.3898" |
| Cylinders | 6 |
| Compression ratio | 9:1 |
| Bore/stroke ratio | 1.124 |
| Block material | cast iron |
|---|---|
| Head material | cast iron |
| Valvetrain | OHV |
| Fuel type | gas |
| Advertised HP | 155 hp |
| Bore/stroke character | 1.124 — oversquare — bore exceeds stroke, which favours higher RPM and larger valves |
|---|---|
| Mean piston speed at 6,000 RPM | 3,390 ft/min — conservative for a street engine |
| Displacement per cylinder | 38.7 ci |
| Static compression | 9:1 — low by modern standards, generally happy on regular pump fuel |
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