ideal quench is good at .040 or less. ultimately your trying to not allow room for the gas mixture to ignite. however, in real world driving applications your never really at the point of needing ideal quench. you may have to back your timing down a few degrees and you may lose a couple of hp. but are your really going to notice the difference? you might if your worried about your top speed or best performance all the time. most of us just want to drive our cars, and whether you have 580 hp or 560hp, you'd never tell by the seat of your pants.