Originally Posted by George Villar
When you post flow-bench numbers for the ported heads, the normal (and I know this because I own a Superflow bench and have 20+ years experience), you record the baseline that the intake port flows at a certain degree cam lift, then record the the new (ported) intake runner results next to the baseline for comparison. When I used to port heads, I used to experiment with a few shapes and cast them in rubber. This meant that we would go through 2-3 sets of heads to test the different shapes - not the port size - the shape is what flows better as we all know. I'm curious to know why you choose to grind away the valve guide completely instead of knife-edging it so that if you opt for a larger set of cams at 14,000+ rpm - the valve stems would remain stable. Was there a reason?
George, in this day and age, you can open the port as far as you want to and then add epoxy in subsequent versions and test various configurations. You'll end up with a series of motors designed for different tracks.
The reality is that it's not about the most power but the best curve, and it's different for each track. Examples might be Miller and Daytona, wide open, Barber, restricted and shaped a bit.
Either way, it's the same initial head porting job.
Anyway, I'm not sure any of this matters in amateur hands these days, what's much more important is proper injector timing because the different fuel choices have such a big vaporization range. With most modern motorcycles way out of optimal injector timing on stock or kit ECU's, proper flow isn't going to help much.
Sort of the small end of a bigger problem I think.