Head porting: Texture differences

[TucsonHooligan]

I'm currently working on the porting on a late model head and had a question about texture. I've worked on 2 stroke Italian scooters for years, and to get the most out of the little engines, we polish the exhaust port smooth as can be, but we leave the intake porting a little rough, about the same as 80 grit sandpaper. The idea behind this being that a slightly rough surface will keep the air/fuel mixture more consistent, keeping it "tumbling", for lack of a better term, and that a slick surface will cause the fuel to stick to the walls of the intake. This is on a two stroke, so the question is, does this same idea ring true for a 4 stroke automotive motor? I polished the exhaust ports up real nice, but am tempted to leave the intake ports alone with the casting surface intact to keep the mixture stirred up while it flows. I hope I described this well enough to be understood. What do you guys think?

 

[rbohm]

8) the vast majority of engines prefer having ports that are slightly rough. one of my college instructors would port the heads as smooth as possible, and then take a medium cutter head and let the porting tool bounce around the intake ports. he would pick up an extra 5hp that way.