01-09-2024, 07:36 AM
Hi Andy
If you raise the CR, and possibly also raise the effective compression by restoring valve sealing etc, you will increase the peak pressure in the cylinders when they fire. Its this pressure peak that generates harsh or rattly noises, especially around 2000 RPM / 30 MPH in top when the throttle is open for acceleration or hill climbing. It's not actually pinking if you are using normal petrol, its octane is way more than needed for a seven even with a "high" compression head.
Reducing the advance a tad will tame the peak pressure without dropping the mean pressure very much. Set the timing to wherever the engine feels happiest on the road.
If you raise the CR, and possibly also raise the effective compression by restoring valve sealing etc, you will increase the peak pressure in the cylinders when they fire. Its this pressure peak that generates harsh or rattly noises, especially around 2000 RPM / 30 MPH in top when the throttle is open for acceleration or hill climbing. It's not actually pinking if you are using normal petrol, its octane is way more than needed for a seven even with a "high" compression head.
Reducing the advance a tad will tame the peak pressure without dropping the mean pressure very much. Set the timing to wherever the engine feels happiest on the road.