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40 Deluxe · 05-14-2013, 01:22 AM

MikeK, Are you sure that less than .020" squish height will cause detonation? My experience has been the opposite; it will lessen detonation. Here's why: After the spark plug fires, a flame front advances across the combustion chamber, building pressure (and thus heat) ahead of it. Under high load/heat situations, this pressure ahead of the flame can auto-ignite the fuel/air mixture in the far reaches of the chamber (the squish area above the piston). So now you have two flame fronts heading towrd each other. When they collide, BAM! detonation! With a tight squish height there is less room for a second flame front to form. Also, with a small squish height, there is greater turbulence as the piston reaches TDC, which better mixes the air and fuel, making for a faster burn (less time for detonation to occur and less spark advance needed).

05-14-2013, 01:22 AM	#4
40 Deluxe Senior Member Join Date: May 2010 Location: now Kuna, Idaho Posts: 3,787	Re: piston/block heigth MikeK, Are you sure that less than .020" squish height will cause detonation? My experience has been the opposite; it will lessen detonation. Here's why: After the spark plug fires, a flame front advances across the combustion chamber, building pressure (and thus heat) ahead of it. Under high load/heat situations, this pressure ahead of the flame can auto-ignite the fuel/air mixture in the far reaches of the chamber (the squish area above the piston). So now you have two flame fronts heading towrd each other. When they collide, BAM! detonation! With a tight squish height there is less room for a second flame front to form. Also, with a small squish height, there is greater turbulence as the piston reaches TDC, which better mixes the air and fuel, making for a faster burn (less time for detonation to occur and less spark advance needed).