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96 ZJ 4.0 / 42RE / NP242 / 4.56 Gears / HPD30 Truetrac / F8.8 Trac-Lok / 2x6 Sliders / Fully Skidded
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Discussion Starter · #1 ·
After just replacing both heads on my project 5.9, I was doing the final torque down of the passenger side exhaust manifold and of course one of the studs snapped clean off about 1/16" below the surface of the head.

For anyone searching in the future, the (4) exhaust studs are 5/16-18 & 5/16-24 x 2.25" long. The 5/16-18 side threads into the cylinder head and the 5/16-24 side receives the conical washer and nut.

After removing the manifold I used a self centering drill bit tool and a left hand drill bit on a 90-degree drill attachment to drill into the stud. The 90-degree attachment was key to avoid pulling the head as it was tight quarters with A/C lines and the shock tower right in the way next to the head. The self centering tool (usually reserved for woodworking) worked great to avoid any threads and keep the hole mostly centered even when drilling at an odd angle. I used lots of WD-40 to keep the broken stud cool and prevent it from being work hardened. After I had a 1/8" hole drilled roughly 1/2" into the stud I tapped a T-20 torx bit into the stud with a hammer. I then used a 1/4" socket to easily back out the broken stud.

Using the torx bit method worked out way better than I had anticipated. The great thing about this method is that if the bit starts twisting in the broken stud you can just tap in one size larger torx bit. Also, if the bit ends up breaking, it can be easily drilled through since it is not hardened like most extractor bits. Lastly, they have become so common and most people have a handful of different size torx bits that came free in a box of screws.

I had a bit of trouble finding a replacement stud locally, no auto parts stores had the exhaust manifold hardware kits or threaded studs in the correct size - 5/16-18 & 5/16-24 x 2.25" long. I was able to find one at my local Ace hardware that was only 2" long but still worked fine.

There wasn't a ton of info out there on this topic so I thought I would share this win for anyone in the future with this problem. I had to refer to the parts catalog to find the correct size and thread pitches of the studs since searching online pulled up some conflicting info.
 

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96 ZJ 4.0 / 42RE / NP242 / 4.56 Gears / HPD30 Truetrac / F8.8 Trac-Lok / 2x6 Sliders / Fully Skidded
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Discussion Starter · #4 ·
Thanks for the response and the great pictures as always, Wingless.

I have attached a screenshot from the 98 FSM showing the location of the bolt, stud bolt (the bolts with the threaded post for the heat shield) and the two threaded studs that accept nuts & washers in the center of each manifold. That's how my 98 5.9 was set up.

I now see a note in the exhaust section saying, "CAUTION: If the studs came out with the nuts when removing the exhaust manifold, install new studs."

I should have replaced the studs from the get go rather than transferring them to the reman heads. The exhaust fasteners had minimal to no rust so I saw no reason to replace them.
 

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When I did my exhaust manifold replacement I replaced all w/ the OEM screws. Several had threaded posts for the exhaust shield, extending out past the hex head. None were studs.

My bad.

Checking my parts listing I found these studs and nuts were ordered / used instead of just bolts, as was previously (incorrectly) posted.

Mopar 0603 4643 Exhaust Manifold Stud 0.312-18 / 0.312-24 x 2.25
Mopar 0603 5184 Stud 0.312-18 / 0.312-24 x 4.125
Mopar 0011 5729 Hex Mounting Nut 0.312 x 24
 

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I now see a note in the exhaust section saying, "CAUTION: If the studs came out with the nuts when removing the exhaust manifold, install new studs."
Don't sweat it. Most of us probably would've done the same thing. Thanks for posting the details, especially the stud specs and the torx bit removal trick.
 
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