Generally what Polyspheric said
I run under 4" bore tight pistons .025
440 6 pack type piston .030- .040
loose pistons .040
aluminum rods and loose pistons.050 but you loose some effect which is made up by race gas or alky
two things
the squish- turbulence mentioned above
and the quench two cold surfaces close together squeezing out the fuel molecules and quenching detonation
low compression motors can use bigger area than High
on a turbo alky build we had to cut the quench area down as we were blowing the fire out- burn pattern on the pistons- took a while to figure out
in addition tight quench helps with timing variations and good/ bad fuel
just gives you more room to tune without detonating your motor
or when you get a load of bad gas
more important in a highly loaded application- say motorhome or boat or towing and less important in a motor that is past the detonation range and running high rpm- and race gas
which is why you could race an open chamber low compression MOPAR but they suck on the street almost the same with high compression and open chamber