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Mercury Windsor specs: 302 ci (5.0L) 8-cylinder, 4.00 x 3.00 in (101.6 x 76.2 mm) bore and stroke, 9:1 compression. Rated 150-225 hp. OHV.
The Mercury Windsor is oversquare — the 4" bore exceeds the 3" stroke by 33.3% — a layout that favors airflow and RPM over leverage at the crank. The 3" stroke does not reach 4,000 ft/min of mean piston speed until about 8,000 RPM, so piston speed is not what limits this engine's revs — valvetrain and breathing are. Each of the 8 cylinders displaces 37.8 ci (619 cc).
9:1 on iron heads is low by modern standards and generally happy on regular pump fuel.
It is one of 24 engines in the Windsor family, sitting between the 221 ci and 351 ci members. 4 factory variants share these dimensions, rated from 150 to 225 hp. Factory fitments include the Cougar, Grand Marquis, Mountaineer and 5 others.
| Displacement | 302 ci / 5 L |
|---|---|
| Bore | 4" |
| Stroke | 3" |
| Cylinders | 8 |
| Compression ratio | 9:1 |
| Bore/stroke ratio | 1.333 |
| Block material | cast iron |
|---|---|
| Head material | cast iron |
| Valvetrain | OHV |
| Fuel type | gas |
| Advertised HP | 150–225 hp |
| Bore/stroke character | 1.333 — oversquare — bore exceeds stroke, which favours higher RPM and larger valves |
|---|---|
| Mean piston speed at 6,000 RPM | 3,000 ft/min — conservative for a street engine |
| Displacement per cylinder | 37.8 ci |
| Static compression | 9:1 — low by modern standards, generally happy on regular pump fuel |
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 |
|---|---|---|
| — | 150 hp | 302 EFI |
| — | 205 hp | 302 HO |
| — | 210 hp | 302 |
| — | 225 hp | 302 HO |