Just couldn't resist-0vertightened & broke Exh pipe stud

[Scott21]

I just could not resist turning the header pipe bolt 1 more time. Stripped it out. Anyone in New Jersey have an Exhust Manifold laying around?

PO installed a bolt where the stud should have been. What size stud should it have been?


Scott

[wesk]

Did you strip the threads on the bolt or the threads in the manifold?

You can oversize the manifold stud hole and switch to a stepped stud. Or you can heli-coil a new set of threads in the manifold. Before you opt to use a stepped stud make sure a stepped stud in the size you need is available.

Original stud was:
3/8-16 NC-2 x 3/8-24NF-2 1 9/16" long.
Superceded to:
3/8-16NC (NC threads 9/16" long) x 3/8-24NF-2 (NF threads 5/8" long) x overall 1 9/16" long.

The 3/8-16NC are the thread size in the exhaust manifold.

To heli-coil repair you need a 3/16NC helicoil kit.

__________________________________________________________

To oversize the hole in the manifold you can drill it out to a 7/16-20NC thread and buy a stud with the same dimensions as the second one above and change the 3/8-16NC to 7/16-20NC.
This would be a :
7/16-20NC (NC threads 9/16" long) x 3/8-24NF-2 (NF threads 5/8" long) x overall 1 9/16" long.

This may be an odd size which is why I said make sure you can find this stepped stud before you commit to going oversized in the manifold hole.

[Scott21]

Thanks Wes, I stripped the manifold. It will thread but will not tighten down.

Scott

[wesk]

You may also consider just removing the manifold and take it to the machine shop for about one hour's labor and be done with it.

[Scott21]

Wes, Was going to take the manifold to be fixed and the whole tab where the stud should have been fell apart.

Scott

[wesk]

I've seen them welded before.

[wilfreeman]

Did you strip the threads on the bolt or the threads in the manifold?

You can oversize the manifold stud hole and switch to a stepped stud. Or you can heli-coil a new set of threads in the manifold. Before you opt to use a stepped stud make sure a stepped stud in the size you need is available.

Original stud was:
3/8-16 NC-2 x 3/8-24NF-2 1 9/16" long.
Superceded to:
3/8-16NC (NC threads 9/16" long) x 3/8-24NF-2 (NF threads 5/8" long) x overall 1 9/16" long.

The 3/8-16NC are the thread size in the exhaust manifold.

To heli-coil repair you need a 3/16NC helicoil kit.

__________________________________________________________

To oversize the hole in the manifold you can drill it out to a 7/16-20NC thread and buy a stud with the same dimensions as the second one above and change the 3/8-16NC to 7/16-20NC.
This would be a :
7/16-20NC (NC threads 9/16" long) x 3/8-24NF-2 (NF threads 5/8" long) x overall 1 9/16" long.

This may be an odd size which is why I said make sure you can find this stepped stud before you commit to going oversized in the manifold hole.

OK, bringing up this old thread because it was as close as I could find to what I was searching for. I am looking for the stud sizes for my M38a1.

Can someone look at the parts manual and get the exhaust stud sizes for me? The ones stated above should be the size for the center studs, but the front and rear ones are longer - like maybe 2 1/16" long?

I removed all the studs from my block (F-head) except for the broken one in the very back. I am planning on moving the body back far enough to get to the broken one tomorrow. Anyhow, I am at work right now so I can't download the parts manual to get the sizes for the studs and wanted to stop on the way home in the morning to save a trip to town.

[wesk]

Stud, S, 3/8-16NC (9/16) x 3/8-24NF-2 (5/8) x 2 3/16. 2ea

[wilfreeman]

Thanks Wes! Now I can stop by on the way home and not have to make a special trip to town to pick them up.