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Mercury 460 specs: 460 ci (7.5L) 8-cylinder, 4.36 x 3.85 in (110.7 x 97.8 mm) bore and stroke, 10.5:1 compression. Rated 365 hp. Rod ratio and piston speed.
The Mercury 385 (460) is oversquare — the 4.36" bore exceeds the 3.85" stroke by 13.2% — a layout that favors airflow and RPM over leverage at the crank. The 3.85" stroke puts mean piston speed at 4,000 ft/min around 6,250 RPM, which is where a production bottom end is generally considered at its limit. Each of the 8 cylinders displaces 57.5 ci (942 cc).
10.5:1 on iron heads is in the range that usually runs on pump premium; iron holds heat, so treat it as the less forgiving side of that range.
It is one of 10 engines in the 385 family, the largest at 460 ci. Factory fitments include the Mercury Grand Marquis, Mercury Colony Park, Marquis and 2 others.
| Displacement | 460 ci / 7.5 L |
|---|---|
| Bore | 4.36" |
| Stroke | 3.85" |
| Cylinders | 8 |
| Compression ratio | 10.5:1 |
| Bore/stroke ratio | 1.132 |
| Block material | cast iron |
|---|---|
| Head material | cast iron |
| Valvetrain | OHV |
| Fuel type | gas |
| Advertised HP | 365 hp |
| Bore/stroke character | 1.132 — oversquare — bore exceeds stroke, which favours higher RPM and larger valves |
|---|---|
| Mean piston speed at 6,000 RPM | 3,850 ft/min — in the range typical of performance street engines |
| Displacement per cylinder | 57.5 ci |
| Static compression | 10.5:1 — in the range that usually runs on pump premium |
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