I am in the middle of replacing the catalytic converter assembly and stuck on the reassembly. The original exhaust header to cat assembly studs were rusted and pretty gumbied up from the disassembling. I could not get the studs out so I bought new Dorman headers that came with the studs and now I have a problem. I cannot find a nut that fits them. I tried a 3/8 x 16 which is what seemed to match up with the old nuts (I only have 2 of the original nuts left), and it doesn't fit all the way down the stud. Also the old nuts DO fit...I am stuck. Any help would be appreciated.
Exhaust Flange Nut size for a 3.8 stock exhaust
- Thread starter fakk1966
- Start date
slowfashow
New Member
wmburns
SN Certified Technician
Try a metric size instead of an SAE size. Also think you are missing the lock washers which is why you can not tighten all the way.
Also, not a good idea to use low grade steel hardware store nuts for exhaust applications. Suggest going to Ford and buying the nuts designed for exhaust duty (bronze/copper I think).
Also, not a good idea to use low grade steel hardware store nuts for exhaust applications. Suggest going to Ford and buying the nuts designed for exhaust duty (bronze/copper I think).
Found it
Thanks for the input, since the original studs were on the car and wouldn't come off, I had matched with the nut. It is an M10-1.50 metric. A M10 -1.50 bolt WILL go on a 3/8-16 bolt which was what originally threw me off but doesn't work the other way (3/8 is just slightly narrower with and almost identical thread spacing) Was able to take the new stud in and match it...was very very close in size.
Thanks for the input, since the original studs were on the car and wouldn't come off, I had matched with the nut. It is an M10-1.50 metric. A M10 -1.50 bolt WILL go on a 3/8-16 bolt which was what originally threw me off but doesn't work the other way (3/8 is just slightly narrower with and almost identical thread spacing) Was able to take the new stud in and match it...was very very close in size.
MustangLX-5.0
Founding Member
Yeah, I would suggest going to Ford, or at least see if the company you got the headers from has a set of nuts to go with those studs. Yes, the nuts are more expensive, but that's because the nuts are torque AND heat rated.. for high strength and corrosion resistance. Exhaust nuts can easily become seized on, stripped or they can bust and/or stretch if the proper type isn't used. That is nearly the hottest section of exhaust, even hotter than the header to head nuts.
When I took my exhaust off one time, I was able to use my air impact wrench. That, along with 3 repeat and wait intervals of PB blaster. All the nuts came off with some work, except for one... in which case the nut never budged and the stud unscrewed instead. Thats what happens when you get overheated cats (red hot). Nut got cooked on there good. THIS is just one of many reasons why you NEED top quality nuts. Even some high grade nuts at the hardware store may not be enough. Those nuts were not designed for exhaust pipes where extreme high temps exist. IF you do use some hardware store nuts, make sure you slap on a good deal of anti-seize compound on the entire length of the stud threads.
When I took my exhaust off one time, I was able to use my air impact wrench. That, along with 3 repeat and wait intervals of PB blaster. All the nuts came off with some work, except for one... in which case the nut never budged and the stud unscrewed instead. Thats what happens when you get overheated cats (red hot). Nut got cooked on there good. THIS is just one of many reasons why you NEED top quality nuts. Even some high grade nuts at the hardware store may not be enough. Those nuts were not designed for exhaust pipes where extreme high temps exist. IF you do use some hardware store nuts, make sure you slap on a good deal of anti-seize compound on the entire length of the stud threads.
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