Head design question

[Onski326]

Need some input on this one here. The bike is listed below as to what it has. I just added a Cool Head to the mix and a head by DNS. So here's my ordeal. When I switched out the stock head for the Cool Head with the 18cc dome (I have a 21cc as well), I feel like I lost bottom end power. I thought for sure that decreasing the cc's would yield better bottom end grunt. This is an XC bike by the way so I'm striving to squeeze every once out of the low end that I can. Anyway, when I measured the Cool Head's domes, they did mic out to 18 and 21 cc. I then did the stock head and got 23cc. The DNS head held 30cc. So I'm at a loss. I have not ran the DNS head for fear of losing even more bottom end. Right now the squish is set to 0.060.
Why would the stock head seem to have better bottom end? Does it have anything to do with the layout of the head design? The DNS and Cool Head both look fairly similar with a broad dish design and the stocker has more of a cup that flares into a dish. I'm sure you guys have seen enough heads to know what I'm talking about. I like the idea of better cooling with the Cool Head but I'm kinda bummed at the loss of power (butt dyno tested at least).
I'm torn. Any ideas or thoughts? I'm running the CR250 head gasket btw.
Can anyone explain the theory behind the head design? As to which design is suppose to do what. Like if one is better for torque and another for top end. I'd be very interested to hear the thoughts on that.

[Bowtie316]

About all I can say on the subject is that the squish band width and squish velocity can change the characteristics of power delivery.  I would start searching google for squish band width and velocity and see if there is information out there.

When I changed out a stock 87 head for a coolhead with 21cc dome, I couldn't tell any difference.

[Onski326]

That does sound like a nice rainy day project. Or in my case in TX, a nice '100 degree day stay in the house' project. I'll look into in and report back unless anyone already knows the meaning to life and can answer this.

[broken1]

Check out MacDizzy, lots of great info there.

[Onski326]

Here are the heads I was testing. Just for reference. The one on the left was the 30cc DNS. The one in the middle was the 18cc Cool Head and the one on the right was the 23cc stocker. I do not have a dyno, but from my testing the last few days, the stocker had the best power before the pipe came on which is what I'm trying to find. It had a snap that was a little more aggressive out of corners than the other two. The Cool Head felt a little flat. Like it needed a little more rpm to pull the same torque. The DNS felt noticeably more flat than the Cool Head out of corners. After the pipe came on, it was kinda hard to tell if there was any differences or not. I think the DNS may have pulled the hardest but only towards the top of the rpm range. The Cool Head and stocker were too close to tell. So needless to say, I put the stock head back on.