I recently just bought a Summit Racing Battery Relocation Kit (SUM-G1200A) my only problem with the whole kit is 3/8" of 1" self tapping bolt that comes with the kit which is just junk. They tell you to drill a 5/16" hole in the frame for the 3/8" bolt to go in. The bolt goes in and doesn't tighten up. Other than that a good kit.

You sure you didn't woller out the hole a little? 3/8 is = to 6/16 so a 5/16 pilot hole should work perfect.

yes because the bolt was tight going in first and than just wouldn't tighten anymore.

If you don't feel like drilling another hole. A cheaper and easy way to get the bolt tight is to put a piece of thin mechanics wire in the hole then thread the bolt in.
But I would think that pilot hole should be a little smaller than that on the instructions sheet. I'd call Summit and talk to them about it. They're really good about customer service. At least for me they have been.

sounds like you just overtightened it and stripped the threads