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Ford 4.9L Six specs: 300 ci (4.9L) 6-cylinder, 4.00 x 3.98 in (101.6 x 101.1 mm) bore and stroke. Rated 115-117 hp, 1979–1983. Rod ratio and piston speed.
The Ford 4.9L Six is close to square: 4" bore against 3.98" stroke, within 0.5%, which splits the difference between a high-revving layout and a torque layout. The 3.98" stroke puts mean piston speed at 4,000 ft/min around 6,050 RPM, which is where a production bottom end is generally considered at its limit. Each of the 6 cylinders displaces 50.0 ci (819 cc).
It is one of 7 engines in the 240/300 Big Six family, the largest at 300 ci. 4 factory variants share these dimensions, rated from 115 to 117 hp across 1979–1983.
| Displacement | 300 ci / 4.9 L |
|---|---|
| Bore | 4" |
| Stroke | 3.98" |
| Cylinders | 6 |
| Configuration | I6 |
| Bore/stroke ratio | 1.005 |
| Block material | cast iron |
|---|---|
| Head material | cast iron |
| Valvetrain | OHV |
| Fuel type | gas |
| Advertised HP | 115–117 hp |
| Years | 1979–1983 |
| Bore/stroke character | 1.005 — square — bore and stroke are within 5%, a balanced compromise |
|---|---|
| Mean piston speed at 6,000 RPM | 3,980 ft/min — in the range typical of performance street engines |
| Displacement per cylinder | 50.0 ci |
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These records share identical bore, stroke, displacement and compression. They differ by model year and factory power rating.
| Year | Advertised HP | Code |
|---|---|---|
| 1979 | 117 hp | 4.9L Six |
| 1980 | 117 hp | 4.9L Six |
| 1981 | 115 hp | 4.9L Six |
| 1983 | 115 hp | 4.9L Six |