Jaguar's published curve
Jaguar's published curve for an 8:1 compression XK140.
Static timing is 10 degrees. Advance begins at 1,200 rpm. 25 degrees of mechanical advance are added up to 4,500 rpm, so 35 degrees maximum. A further 8 degrees of vacuum advance is added at light throttle.
The curve developed for WPK38
Developed on the rolling road at Automark, Stokesley, with a knock sensor on the block. Advanced in 1–2 degree steps at 500 rpm intervals to maximum power, then backed off two degrees as a safety margin.
| RPM | Advance (degrees) |
|---|---|
| 500 | 12 |
| 1,000 | 12 |
| 1,500 | 19 |
| 2,000 | 23 |
| 2,500 | 27 |
| 3,000 | 32 |
| 3,500 | 33 |
| 4,000 | 34 |
| 4,500 | 34 |