Lets talk about why "squish" has a significance to the out put of an engine. Squish improves the stability of combustion. Its known to achieve more compression is to simply reduce the combustion chamber. This is done by block and head decking, piston height, rod length, head gasket thickness and so on. Modifying the chamber is another way, but lets keep this simple. Comression is essentially what we power hungry Americans are chacing after wether it be by N/A or forced induction. But an inherent flaw gets created in are search for more compression. ..pre-ignition! Pre-ignition refers to an undesired combustion before a desired spark location of the piston. In other words pre-ignition is the fuel self combusting at the wrong time. A static compression ratio is the mathematical given space of total compression area. This area is made up of the top of piston at the top of its bore, crushed gasket thickness, and head chamber. Try to imagine an engine cut away view. Now...a static ratio of 13:1 with a squish distance .050" is not the same as 13:1 squish distance .020". Squish distance refers to the distance amount between the piston crown and head surface. The .050" will be more prone to pre-ignite than .020". Lets talk about what happens in the chamber. The intake valve opens, the mixture rushes in as the piston travels down creating a tornado vortex swirl keeping the mixture homogeneous or uniform throughout. As the piston travels up its compression stroke, that mixture gets moved around again untill the piston starts to slow down as its nearing top dead center and the mixture slows as well but being compressed. A mixture not in motion will self combust and if there is room between the piston and head pre-ignition will be more probable. But in a last attempt to get that mixture moving at the pistons slowest rate, ...we reduce pre-combustion by squishing the mixture by using the moving pistons crown pressing up to the heads flat surface area of the comustion chamber. This causes the mixture to suddenly move before it has a chance to become stagnant or still while being compressed. Still motion gas being compressed pre-ignites. This squished mixture rushes into the only open available area, the chamber thus creating a tighter package to also improve flame travel time. If the more space between the head and piston ATDC the more lame the cumbustion becomes. The least is the opposite to the point of the piston kissing the head thus stabilizing the combustion to withstand higher compression.