proper combustion chamber design, pre-ignition can generally be eliminated by proper spark plug selection, proper fuel/air mixture adjustment, and periodic cleaning of the combustion chambers. Causes of pre-ignition Causes of pre-ignition include the following: Carbon deposits form a heat barrier and can be a contributing factor to pre-ignition. Other causes include: An overheated spark plug (too hot a heat range for the application). Glowing carbon deposits on a hot exhaust valve (which may mean the valve is running too hot because of poor seating, a weak valve spring or insufficient valve lash) A sharp edge in the combustion chamber or on top of a piston (rounding sharp edges with a grinder can eliminate this cause) Sharp edges on valves that were reground improperly (not enough margin left on the edges) A lean fuel mixture or excessive amount of oxygen in the combustion chamber An engine that is running hotter than normal due to a cooling system problem (low coolant level, slipping fan clutch, inoperative electric cooling fan or other cooling system problem) Auto-ignition of engine oil droplets (Can be solved by using an oil catch tank) Insufficient oil in the engine Ignition timing too far advanced Too much air/too little fuel (octane) to withstand pressures (too much air causes too much pressure for the octane to handle, too little fuel reduces the octane to handle the pressurized air) Detonation induced pre-ignition Because of the way detonation breaks down the boundary layer of protective lubricant surrounding components in the cylinder, such as the spark plug electrode, these components can start to get very hot over sustained periods of detonation and glow. Eventually this can lead to the far more catastrophic pre-Ignition as described above. While it is not uncommon for an automobile engine to continue on for thousands of kilometers with mild detonation, pre-ignition can destroy an engine in just a few strokes of the piston. References Engine fuel system technology