Having a quench area in the combustion chamber is a wonderful thing. The 426 Hemi didn't have one, and it had issues at low speed and at low flow rates because of it. The optimum quench area is going to force the intake charge across the chamber in a chaotic fashion, causing turbulence and better burning. It also has the added effect of cooling hot spots and controlling detonation. Most engineering studies have determined that .020" is best, but most engines do well with about .040" of clearance in the quench area. Remember that the smaller the vertical space in your quench area, the more forcefully the mix will be squeezed out. High compression domes in the pistons will negatively impact the quench flow, and some builders will actually carve a notch or groove into the dome, in order to keep some of this very positive effect alive. I have noticed no issues in my 10.75:1 383, but tuning and piston construction may also be factors. I managed to get this engine to live on pump premium gasoline (91 octane at this altitude), but more timing and more power were available to me with more octane available. E-85 has been very easy to work with in this engine, and the cooler burn, higher octane (105-110), and high-detergent qualities of the ethanol fuel are wonderful benefits. Rather than fight with the tune, and accepting the level of performance it allowed, I can tune for power, with little fear of hurting the engine with this fuel. I gained 20 BHP, and 2 MPG by switching to ethanol.
