About three weeks ago I picked up a shopping bag of them from under a tree at my mom's house. Then I set them on a table under the eaves so that they would dry out. I didn't bother to husk them at all. Simply set them in the table away from any rain. So today I picked them up in order to give them a try. The husks were completely dried.
I first started the fire my usual way, using twigs and a bit of paper. Then I burned a couple faggots of twigs in order to get a bed of embers before adding nuts. Then I put about a quart of nuts atop the embers. It didn't take long for them to start slowly burning. Once the nuts started to burn, they burned hot and bright.
So I conclude that dried kukui nuts do indeed make suitable fuel. Though free for the taking, it does take time to pick them up. And stooping down to reach them. I don't know if they would still burn as well if they were stored for months before burning, but storing for a month or so seems to be fine. So here's another thing I'll need to experiment with. How long will they retain their oil and be good for a hot fire?
So where did I get the idea to try burning these nuts? From the ancient Hawaiians. They used these nuts as a torch, skewering them on a stick then setting them alight. The nuts contain oil that readily burns. So I knew that historically they were good for burning for light, but I was surprised to see how much btu's they generate. Hot little buggahs!