Never take a dremel to an aluminum head. Its too easy to trash the head. Also they are fine stock no need to mess with them unless your trying to make over 500 hp. Electric die grinder is what you need but not dremel you need low speed for aluminum heads. high rpm of dremel will eat into the head to fast. Air power is no good for alum heads either same issue and also stalls at low rpm.
@ssmonty that was a swirl device you removed. The air must spin around the valves and into the combustion chamber. that is why they leave the sharp edge around the seat pocket. you can clean it up but not take it out all together. Unless replacing it with a real full on pocket port job. Edelbrock did not cut major corners they just didnt pocket port the heads. You didnt either. Rule of thumb for aftermarket heads is only port them if you have too by class. Other than that buy the next size up. Once you max out your heads then maybe go back for the 10 hp the manuafacture left on the table.
@O/P leave your heads factory. Have the valves checked to see if they are seating up. other than that just leave them be. They can be ported and could use some work from the factory. But you will make 400hp without going to the trouble.