Topic: 66 HiPo Exhaust Manifold stud hole thread size?

[Morsel]

Hi all,

As the title states, wondering if anyone knows the thread size for the 66 289HP exhaust manifolds studs that thread into the manifolds? I need to chase the thread on the manifolds for new studs as one is extremely tight and not allowing me to put the stud all the way in, figure it would also be a good idea to chase all of them anyway. I looked through Jim's hardware guides in the library and only saw the nut side which is 7/16 - 14.

Anyway, any help would be appreciated.

Thanks as always,

Jason

[jwc66k]

The stud must be tight so it won't come out if the nut gets stuck. It is referred to as an interference fit. "Chasing" the hole with a tap will make it way to big (which answers a lot of questions as to why the stud came out too easy). To install, try the old "double nut" on the exposed threads and tighten as best you can. WD40 may help as it should burn off when you fire up the engine. A technique I have wanted to try is to heat the area at the holes with a torch (that's how you get the stud out) and insert the cooler (aka smaller dia) stud. Candle wax is another technique used to get a bolt and nut apart, so it may be another "solution" to get the stud in.
This thread should apply to all years exhaust manifolds.
Jim

[Morsel]

The stud must be tight so it won't come out if the nut gets stuck. It is referred to as an interference fit. "Chasing" the hole with a tap will make it way to big (which answers a lot of questions as to why the stud came out too easy). To install, try the old "double nut" on the exposed threads and tighten as best you can. WD40 may help as it should burn off when you fire up the engine. A technique I have wanted to try is to heat the area at the holes with a torch (that's how you get the stud out) and insert the cooler (aka smaller dia) stud. Candle wax is another technique used to get a bolt and nut apart, so it may be another "solution" to get the stud in.
This thread should apply to all years exhaust manifolds.
Jim

Hey Jim, thanks for the response. Yeah I checked it again this morning and it seem as they are indeed 7/16 x 14 in the manifold, screws in smooth using the "nut side" side of the studs, and then noticed that the threads are sort of "Blunted" on the manifold side of the studs which, I guess makes them go in super tight. Anyway, I can get three of them in, but one is just not letting me get it all the way in no matter what I try, I've already tried the double nut method, it's how I got the others in, and used the torch method too. I'll try some candle wax next, appreciate the tips and I'll give them ALL a try

Thanks as always,

Jason

[mtinkham]

If it were my car, I would chase the threads. Better to have the stud fully engaged then take a chance of breaking it off or cracking the manifold.