This I just an idea. Throwing it out there for shots and giggles.

Have a sandblaster and work at a tire shop with a bad *** compressor.
Last time I blasted I burnt out the nozzle flow stop.
Did a quick fix with a grade 8 u-bolt nut welded on.
After I finished blasting I noticed the blaster had eaten away some of the nut.

So I tested it and found it could cut it in half in 5 min.

Now seeing as cast is weaker could I use a sand blaster to port a head.
I know the guides and seat would need work after but the sand would cut smooth and create good flow posibly.
Have a useless set of heads I should try it on.

 

Must be one heck of a sand blaster.

Could be a great way to polish but not to port, porting is shaping and needs more control then you can get with a sand blaster. Better off with a die grinder.

 

also, if you know nothing about porting and polishing you can destroy your heads. If this is a street engine port the intake and carry it in no more than 1 inch and leave the rest alone, you need a ruff surface to help the gas and air to mix (tumbling) it helps for better atomizing.You can do a little bowl blending under the intake valve, take out the high casting parting lines and leave it. The exhaust you want as smooth as you can get it.

 

+1.. Leave the intake side alone unless you got a flow bench and really know what you're doing, but hog out the exhaust side as much as you dare paying particular attention to the roof of the port and blending the bowl into the port. And leave polishing to the Chevy guys.. it actually hurts flow by eliminating the laminar air layer that sticks to a rougher surface.