and a smoother surface does this much better no one particular place for heat to build up. However before that one place gets to disipate heat more heat is introduced into the equation on the very next compression stroke. As far as insulating properties of carbon goes if it had the same insulating properties as the aluminum then yes carbon could build up in the pits causing smoothness and more even dissipation of heat however because it doesnt have any insulating properties the heat goes right through it causing hot spots in the surface of the metal. Its the same concept why the rollerwaves are so damn smooth and why the edges of the valve reliefs are rounded.