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Message: <blockquote data-quote="Burninrock24" data-source="post: 1175650" data-attributes="member: 18179">Whatever you do, don't touch the port floor. Professionals raise the floor actually, lowering it kills the flow. You can clear up some of the shrouding around the valves, and re-lap them too while you're at it. Because believe it or not, the highest velocity air flow happens at very low lift, and at low lift the air is interacting most with the valve, valve seat, and the surrounding area in the combustion chamber. Low lift flow is incredibly important. The port should never be larger than a gasket so it's okay to use that as a rule of thumb. Don't get too ambitious when porting around the valve stem either, get as fine of a wedge shape as you can and leave it in a teardrop shape almost. Otherwise there's a large negative pressure zone behind it. That's a no no. If there's anything that you should keep in mind all the time when porting is that air is very heavy and doesn't like moving. So make as smooth of a path for the air to travel through.</blockquote>