I accidentally cross threaded a header bolt the other night. Should I try chasing the tread or should I leave it? The bolt will tighten its just a little sideways. If I should try cleaning it up what size tap is it?

 

Threads are 3/8-16. That is a touchy call. If the bolt is fully threaded and tight now (crooked), removing it and chasing the threads out straight might make the hole too large and unusable. If it is in a spot where there would be room to heli-coil it, then you would have a back-up plan.

 

Happened to me also. But it was only 2-4 threads in.. I just got a tap and carefully turned it and got it to where the bolt went back in no problem.

 

First I'd try to just remove it and put it in right (assuming it's not screwed in real far.) If that won't work, chase it and go to a 1 inch long bolt just to be safe.