I've been fine over 14k ft with one day to acclimate before and I've also had headaches at 8k ft. I've also done 3 14ers over 3 days only to get AMS on the fifth day while lower at camp. AMS is a fickle mistress and one of the banes of my trips. For me, it's always been very hard to know when it'll rear its ugly head.
Two hikers had previously summited Whitney with AMS problems. One did it with no acclimation as a day hike. The other two (myself included) are prone to the headaches. By the end of the trip, all of us had headaches, with the two that hiked Whitney with no symptoms stopping at Chicken Spring Lake. I am really interested in what forum members will have to say about our situation; more on this later...
Here are a few of my favorite pics from the hike.
The rest can be seen on my website.
Cirque Peak via Cottonwood Pass Trip Report, May 17-18 2014 The trip report will be posted on this page also. I am having issues with my web server, so the page may load slowly.