Originally Posted by ChevroletSS
Ill port them myself. Now I have practiced porting on heads for endless hours but what I still dont get is how Im supposed to tell if I made all the runners the same. I mean its very possible that by doing it myself that when Im done none of them will be the same. Does it matter if one flows just a little differently than others and so on?????
First is the needing of a flow bench to tell it your makeing improvements or causing degradation. In a simple sense and especially with older heads (think pre GT40P, Magnum, Vortec) it was pretty easy to improve ports. This was simply streamling the huge guide bosses and blending the rough cut of the upstream lip ahead of the seat into the wall. This make a marked improvement that was felt when you stepped on the throttle. Modern heads are much more refined in this area today so there is less impact by massaging this zone.
When you get away from the port pocket things are much more subtle, therefore, it is easy to degrade the overall flow. What seems logical to the eye is most likely not where the flow will or wants to go. Most people reporting here state that there is little to be gained by working the port between the manifold face and the turn into the pocket. This really isn't factual, but this is an area where it is easy to do more harm than good. To tease this out you really need a flow bench and a decent understanding of how gasses respond in a physics sense. There are plenty of web sites that lead you into building an inexpensive flow bench using little more than a decent shop vac as a power source.
As far as getting all ports to match the old fashion way was to arrive a good test port then make templates of the port at critical points. The uncut port is ground at the same points to fit the templates then the material between the template stations is ground to smooth connection between these points. There are people on the web that sell templates for known port shapes.