For everybody's better good... Porting is a very individualistic action. You will find very few even top level porters that will do exactly the same thing from start to finish. So long as the results are what the builder/ported wants, there is no "right" or "wrong". I'm trying to avoid any of the BS that sometimes occurs on other sites when getting into these subject areas.
that being said... here's my thoughts on what I do and why.
I stole these pics off Ryan's to show a couple differences. I tend to leave my heads more like what Roppa shows around the guide and bowl, for the same reason. On more "flat out" type deals, I will do more. By tapering the merge all the way back to the long side of the bowl, it hepls low lift, and can hurt mid and upper. The way I understand it you're basically extending the turbulance around the stem, out to the seat. It helps with low lift and wet flow. But as the valve opens further, and ari speed increases, things get "noisey" in terms of flow. Taken to the extreme, this is one of the reasons heads like the Vortec chevies work incredibly well for small cam, low rpm stuff, but cannot be made to work well in higher rpm applications. In Ryan's port pics, you can see the 70° throat cut my valve jobs have (the really wide flat machined area in the unported pic). I will leave about 1/8-1/4" of that visible and enlarge the bowl from there. You can also see in his "ported" pic, the merge of the guide is not right to the edge of the long side of the bowl. He brings the two columns of air together closer to the stem, and leaves a bulge to smooth out the flow adjacent to the stem. Picture two hoses running. One pointed straight, the other at a 40° angle so the streams slam into each other. At low pressure and flow, they just kind of swirl together. Turn up the pressure and volume, and they end up bouncing off each others and going helter skelter. That's how the air flows thru the two high speed toughs next to the guide. In a facotry head, you will almost always fin more residue on the deeper, narrower side of the guide before you clean them because of flow imbalances and not enough speed thru those areas. I work to improve that balance and speed up the air thru there. I dont want it slamming around at the seat. I'll see about getting some pics and volumes off the 346s outside. Maybe that will help...
