polishing the chamber and exhaust is OK to do but don't expect measurable gains. If you get a chance or are interested do a web search on "laminar" flow in intakes. Basically if I can explain this right in a short sentance or two, a smooth surface places drag on the air pasing over it. Think of many thin layers of air from the wall to the center of the runner. The one closest to the wall has the most "drag" on it from the wall and the layer above that has drag placed on it by the first layer (becasue they are in intimate contact from layer-to-layer) and so on into other layers of the runner. With a rough surface, the air "tumbles" in the first layer or two and creates tumbling "air bearings" that break up the drag on the rest of the layers. So, having a slightly rough surface is better for the intake side. The exhaust is different because the gas is much hotter (less dense, less drag) and is being pumped out rather than drawn in (same reason intake valves are bigger than exhaust). Polishing the chamber reduces the chance of hot spots that can create detonation and it inhibits the formation of carbon buildup.
I have ported numerouse heads and have ported both int & exh. But I concentrate on the exhaust ports when polishing.
