I had used an allen key bolt into my heads for my headers because it was literally the only bolt that would fit because of the primaries. I can't figure out what size it is, I have both metric and standard. Is it possible that the heat caused the inside points to round off? The thread size is the same as the stock manifolds. I just put some ARP's in.

 

The only thing that would cause the points to round off would be using the wrong key.