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In the elusive Car Craft Vortec porting article (which has been basically deleted by mistake; the website only shows the first paragraph and photo out of a series that used to be 15 photos.), they measured the following flow increases with a port job similar to mine but a little better (they opened the pushrod pinch, etc.)
Notice the negligible gains on the intake, and the gigantic gains on the exhaust. Here's what their exhaust port looks like:
Porting Tips
It's the hardest area to reach because you have to reach so far in, yet be careful not to bump the grinder on the valve seat. My new 6" burr exposes the major flaw in the Harbor Freight $40 die grinder - it makes it wobble so bad as to be totally unusable (and dangerous). I cut 2" off the shank and it got better, and I used it on a low speed setting. It sucked, and I encourage anyone doing this to find a small radius burr (1/4"-3/8" max, mine was somewhere around 3/8" or maybe a little bigger). I had to carefully use one of my other 2" burrs to come in from the top which was next to impossible with such a short length.
By mistake, I also hit the top edges of the valve guide boss on several ports. However I dont think this really matters because on race heads they heavily grind down the valve guide. If you want to see an amazing small block race head that flows 450cfm, check this out.
