I'll tell you exactly why it won't fit, try it on a dohc d series, it'll fit like a glove. A lot of those eBay ones ship you the 1st gen header. You need to send it back, get a refund, and order one for a 3rd gen, it'll fit perfect. Trust me, I had this issue twice before I learned what the problem was. And let me guess, the top piece fits (it's a two piece header), but the bottom one can't clear, it'll seat one edge, but is at a crappy angle and doesn't seal the other two bolts? Sell it to a friend with a zc motor or a d16a1, and buy a name brand header, best advice from someone who has dealt with it a few times.