after installing the new headers on my car I am having an issue with the bolts not going in all the way in both from the cat end and the block end and I am afraid of snapping them from using too much force. The thing is they came out very easily without even having to use penetrating fluid but now they are giving me troubles going in, why is that happening and how can I fix this?

  • Can you provide more information? Are you talking about nuts, bolts or studs? Are you sure you haven't cross-threaded something? What happens if you loosen everything up and try tightening each fastener a little bit in a star pattern?
    – Bob Cross
    Commented Feb 5, 2017 at 19:32
  • 1
    If these are bolts, are you sure the holes you're putting them into are clean of debris and fluids? Are you sure you're using the correct fasteners? If you got them mixed up (say a coarse thread bolt for the fine thread bolt of the same thickness bolt), it would start in the hole, but not tighten down correctly. Just spitballing. Commented Feb 5, 2017 at 19:40
  • I am talking about the nuts. Would cross-threading make the nut not go all the way in even if there is still space on the stud?
    – method
    Commented Feb 5, 2017 at 19:41
  • @Pᴀᴜʟsᴛᴇʀ2 I am using the same nuts that were on the old one
    – method
    Commented Feb 5, 2017 at 19:42
  • 1
    Are the flanges on the new headers thinner than the old manifolds? Also, can you post a pic?
    – Mobius
    Commented Feb 5, 2017 at 19:48

2 Answers 2


You say it is nuts going down on studs? Probably because the flange on the new headers is thinner than the flange on the originals. So the nut is having to run down farther down the stud. Essentially entering a zone where "no nut has gone before" which is thick with gunk or rust.

Run a thread-chaser or tap down each of the studs, should clean that up.

  • Yes but they are not even going half way in, like I said in a comment even if the header wasn't there the nut wouldn't screw in. It is very hard for some odd reason
    – method
    Commented Feb 6, 2017 at 1:03

Okay so the issue was that I mixed the bolts that connected the exhaust manifold to the catalytic convert with the bolts the connected the manifold with the block. apparently they are different despite looking identical and thus they wouldn't screw in all the way. Thank you every one

  • 1
    Thanks for getting back with a resolution. I was curious to see what the issue was
    – Zaid
    Commented Feb 7, 2017 at 8:31

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .