See other engines in this family
Jaguar XK 4.2 specs: 259 ci 6-cylinder, 92.1 x 106 mm (3.6250 x 4.1730 in) bore and stroke. Rated 265 hp, 1965–1979. Used in the Jaguar E-Type and Jaguar XJ6.
The Jaguar XK 4.2 is undersquare — the 4.173" stroke exceeds the 3.625" bore by 13.1% — a layout that trades peak RPM for leverage and torque low in the range. The 4.173" stroke puts mean piston speed at 4,000 ft/min around 5,750 RPM, which is where a production bottom end is generally considered at its limit. Each of the 6 cylinders displaces 43.2 ci (707 cc).
It is one of 2 engines in the Jaguar 259ci family, all of them 259 ci — the differences between them are in compression, heads and rating, not displacement. 15 factory variants share these dimensions, rated at 265 hp across 1965–1979.
| Displacement | 259 ci |
|---|---|
| Bore | 3.625" |
| Stroke | 4.173" |
| Cylinders | 6 |
| Configuration | I6 |
| Compression ratio | 7.5–9:1 (published figures vary) |
| Bore/stroke ratio | 0.869 |
| Fuel type | gas |
|---|---|
| Advertised HP | 265 hp |
| Years | 1965–1979 |
| Bore/stroke character | 0.869 — undersquare — stroke exceeds bore, which favours low-end torque |
|---|---|
| Mean piston speed at 6,000 RPM | 4,173 ft/min — in the range typical of performance street engines |
| Displacement per cylinder | 43.2 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 |
|---|---|---|
| 1965 | 265 hp | XK 4.2 |
| 1966 | 265 hp | XK 4.2 |
| 1967 | 265 hp | XK 4.2 |
| 1968 | — | XK 4.2 |
| 1969 | — | XK 4.2 |
| 1970 | — | XK 4.2 |
| 1971 | — | XK 4.2 |
| 1972 | — | XK 4.2 |
| 1973 | — | XK 4.2 |
| 1974 | — | XK 4.2 |
| 1975 | — | XK 4.2 |
| 1976 | — | XK 4.2 |
| 1977 | — | XK 4.2 |
| 1978 | — | XK 4.2 |
| 1979 | — | XK 4.2 |
2 factory vehicles, 1965–1979. Each year opens that model's engine table.