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Mercury Windsor (1969–1979) specs: 351 ci (5.8L) 8-cylinder, 4.00 x 3.50 in (101.6 x 88.9 mm) bore and stroke. Rated 135-250 hp, 1969–1979.
The Mercury Windsor (1969–1979) is oversquare — the 4" bore exceeds the 3.5" stroke by 14.3% — a layout that favors airflow and RPM over leverage at the crank. The 3.5" stroke puts mean piston speed at 4,000 ft/min around 6,850 RPM, which is where a production bottom end is generally considered at its limit. Each of the 8 cylinders displaces 43.9 ci (719 cc).
It is one of 24 engines in the Windsor family, the largest at 351 ci. 14 factory variants share these dimensions, rated from 135 to 250 hp across 1969–1979.
| Displacement | 351 ci / 5.8 L |
|---|---|
| Bore | 4" |
| Stroke | 3.5" |
| Cylinders | 8 |
| Configuration | V8 |
| Bore/stroke ratio | 1.143 |
| Block material | cast iron |
|---|---|
| Head material | cast iron |
| Valvetrain | OHV |
| Fuel type | gas |
| Advertised HP | 135–250 hp |
| Years | 1969–1979 |
| Bore/stroke character | 1.143 — oversquare — bore exceeds stroke, which favours higher RPM and larger valves |
|---|---|
| Mean piston speed at 6,000 RPM | 3,500 ft/min — conservative for a street engine |
| Displacement per cylinder | 43.9 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 |
|---|---|---|
| 1969 | 250 hp | — |
| 1970 | 250 hp | — |
| 1971 | 240 hp | — |
| 1972 | 164 hp | — |
| 1973 | 168 hp | — |
| 1974 | 162 hp | — |
| 1975 | 148 hp | — |
| 1976 | 152 hp | — |
| 1977 | 149 hp | — |
| 1977 | 161 hp | — |
| 1978 | 144 hp | — |
| 1978 | 152 hp | — |
| 1979 | 135 hp | — |
| 1979 | 151 hp | — |