Performance mixed with fuel economy!?

Rat Bastid said

After years of screwing with this stuff, I can say unequivocally that the surface finish of the combustion chamber has zero effect on detonation or detonation resistance. In fact, I can (and do) suggest that you polish the chambers to get them to equal size and then use a burr finish on them.

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Interesting, guess I was thinking about potential hot spots but typical open-chamber LA heads don't really have any pointy edges sticking out (compared to say a 302 318 head). What is the benefit of the burr finish, does it help improve mixing of the intake charge during the compression stroke?

My understanding is aluminum heads are more detonation-resistance because the much faster heat transfer makes the combustion chamber surface "cooler" between power cycles and doesn't transfer as much heat into the intake charge as the piston comes up on the compression stroke. But you don't actually lose any combustion efficiency like the old myth claims because there simply isn't enough time in a power stroke above about 2200 RPM to allow any real amount of heat transfer to take place while the mixture is burning. I just figured the smoother and more consistent machined surface finish aided in minimizing heat transfer partly due to the *slightly* reduced surface area.