Slight road block mounting exhaust manifolds, are studs tapered?

[weider1717]

Hey guys, I put all new correct oem hardware on the manifolds new exhaust studs, bought new bolts that screw onto the studs and new springs.

question is are these studs tapered? when I try to screw on the new bolts to the studs they go a little way then stop like they're tapered but the bolts are a old part number so want to be sure they are correct.

the old bolts also do the same do part way then stop so wanted to make sure they are supposed to be like this.

sound familiar to anyone thats been down this road?

thanks!

[cadillac_al]

I think the bolts you are talking about are called nuts. Are they brass? Sometimes they do go on a little hard after the first couple threads and I think that's normal.

[Corts60]

Originally Posted by weider1717

Hey guys, I put all new correct oem hardware on the manifolds new exhaust studs, bought new bolts that screw onto the studs and new springs.

question is are these studs tapered? when I try to screw on the new bolts to the studs they go a little way then stop like they're tapered but the bolts are a old part number so want to be sure they are correct.

the old bolts also do the same do part way then stop so wanted to make sure they are supposed to be like this.

sound familiar to anyone thats been down this road?

thanks!

Sounds like maybe you have metric/SAE fasteners mixed up. I would check the thread count with a thread gauge or tap.

[raceman6135]

The studs aren't tapered, but it's quite possible that you have a type of self-locking nut.

They come with the one part of the nut slightly pinched inward, toward the stud. This makes them difficult to install as you'll need a wrench for all but the first couple of threads. This pinch, however, also keeps the nuts from loosening off. Because the exhaust gets so hot, a Ny-lock nut would not work, and lock washers only work if you can tighten down the nut completely. Often, exhaust nuts can't be tightened down completely because they use short springs over the studs to keep the exhaust tightly sealed, but still allow a bit of movement as the engine moves on its mounts.

Here's a pic of a pinched-style lock nut that you may be using:

[weider1717]

these are THE ones I bought and trying to install see link: http://www.ebay.com/itm/221737968728...ht_2996wt_1128

the book shows part #11517996 should be used however these ones I bought should be the same thing as 11517996 part number is what replaced the part number I bought.

thats why I am questioning things making sure what I bought is infact the same as 11518996. But I think you're right it's a lock nut can anyone confirm? Want to get this finishe this weekend!

[kalbert]

I am suspect that that is both metric and a lock nut. It appears to be squashed in an oval shape, and list of vehicles it fits leads me to believe its metric thread.

[cadillac_al]

I agree that those may be metric based on the vehicles listed in the ad. GM was about 90% metric by the 90's. Your best bet is to get the brass nuts made for exhaust studs in the Help section of most parts stores.

[raceman6135]

Ah yes, as others have stated, that nut you listed is metric: M10 x 1.5. So if you're trying to mate that to an exhaust stud/manifold from an earlier SAE configuration, you'll have even more problems than just the locking function.

Sorry, I didn't see what you're working on. Do you know what thread your exhaust stud is, or what year the exhaust manifold is?