I will be able to tell you what a ported ones flows in a couple of weeks. I have a flow sheet from a regular SOHC I have ported and the magnum will out flow it easily. my regular, ported SOHC flowed 185 cfm at .350 lift at 28" on the exhaust and 232 cfm intake at .350. The intake is the same between magnum and sohc. I have several to compare to at my shop.
It hasnt been opened too wide, a friend of mine whos been porting heads since the 70s is doing it for me. We may add a little tig weld to the #1 exhaust floor, there is a low spot where the egr hole was cast shut.
You can clean up any imperfections, I have found better flow going wider than taller on the neon heads. The only exception was the SOHC head (Not the Magnum) That little buggar needed all the help it could get, but even then, I ended up going alot wider than I did taller. The magnum just has a better designed port. You want to make sure you cleaned up the exhaust bowl area good too. They too seem to have the nasty ridge around that needs to be tapered down.
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