There we go.  So I ovaled it out and radiused the transition into the runners a little.  This work was done with a dremel.  If I had a regular die grinder to use at the time I would have completely ovaled it.  The dremel is doable but it's slow going.  Carbide burs are available from many industrial supplies for 1/8" tools, such as a dremel.  This helps a lot with material removal.  I think my tool list was carbide burs, a  grinding stone, 60 grit sanding rolls and fiberglass reinforced cut off wheels.

I noticed an increase in power, particularly in the higher revs.  Before doing this, the holes were stock size, and the Edelbrock 600 was restricted and then there's the turbulance because of the step, etc.  I never had it on a dyno or a flow bench but it definitely felt stronger.

I did a clean up on the runners.  I got them to about a 60 grit finish but there was no real porting in that area.

There is potential.  I seem to remember seeing flow figures in Y block magazine at some time for professionally ported vs. stock.

      Read what doug said, this is the classically accepted method, and it seems to work pretty well. The Blue Thunder is of course, lighter and flows somewhat better. But the iron intake works pretty good. Maybe better on the street.

A 1/8" Dremil tool must be awfully slow there is quite a bit of cast iron to chew through.  I like a 1/4" electric die grinder with carbide tools. 

 There is a case to be made against polishing which is that a rougher surface provides more area to evaporate fuel and therefore less liquid fuel gets into the cyl.  I subscribe to this idea and do not polish intake systems.  My guess is that a sandblast rough is about optimal.

              Also, laminar flow is aided by the rougher surface. Makes the air against the walls act as a bearing for the main air column. On the ehaust side of the Head (subject change) we do polish for the opposite reason, less surface to conduct heat back into the cylinder head.

      Good question, I'd think Dennis somewhat right, but I've seen some pretty "Gooey" lookin' intakes. I think in most cases the engine heat cooks the blowby into a black "GOO". The reason it's hard to answer Daniel is that we all assume the Air fuel mixture is a nice even mixture. Not so, fuel drops out on sharp corners from velocity, it runs down the bottom of the manifold in little rivers. Drops out, gets picked up again. Real wet flow testing with cut away or quartz walls shows a real complicated mess. Anything we can do to keep fuel in suspension helps big time.  This is the reason injection picks up MPG and horsepower. Also helps emissions by keeping the mixture close to what's needed. Also injects the fuel close to the intake so it doesn't puddle all over the place.