Good question Bruce, and I track this line of thinking. Opening the barn door too wide? These are ~130" motors and in the V8 world that is a 520". We are asking for 6500 rpm. Reality is dynos are abundant with the SE 1.0 heads and they are not much, if any, better than the stock heads with similar builds. What I didn't mention is testing at 28" WC these SE heads howled like a banshee at all higher lifts and the pressure gauge was wandering wildly as well. Ear plugs mandatory. I did find the source and it will take removing some of the touted added material to get the port to be stable. Localized hot spots are not any better than low velocity, and probably worse. Like a lot of Harleys offerings "HD" half done. Keeps guys like me in business. The springs appear and measure to be the same as stock, same pressure and coil bind as stock. If I was a consumer looking at and evaluating the value of $1200 heads the dynos and specs would send me looking elsewhere. Valve sizes are stock, chamber untouched, and the hidden issues.
I will get a chance to look at the SE Extreme CNC heads and I expect a very different picture. Those heads use the same casting to start with but have opened up the throats and other features like +1mm valves and in real world work pretty well.
Here is a typical dyno with my ported heads. This build has been repeated several times and on other dynos has not made less than 155 hp and a few have over 20K miles without issue. Owners report fantastic manners and driveability and no pinging.
