Engine Rebuilding & Engine Management

Broken Exhaust Stud Removal


So you just got your ride almost roadworthy, just refreshed your cylinder head, put on some new headers and you’re torquing down that last exhaust stud nut and snap…$^&%#@! You are probably kicking yourself for reusing 40+ year old exhaust studs because they looked okay, but this is beside the point now. Let’s go over some ways to extract it.
Best case scenario is that there is something left to grab onto with either vice grips or a stud extractor-like tool or socket. This is fairly straight forward, it’s probably best to go ahead and remove the headers again so you can gain better access. Once removed, you should be able to easily extract the stud since there is no torque on it. If it is stuck in the head and not moving, you might need to get a little creative with some strong vice grips and soaking with some liquid penetrant.

The worst case scenario is that it snaps off even with the head or there is not enough of the stud to grab onto it with anything. This was my scenario, so I had to get really creative. I contemplated having to remove the cylinder head, but I knew there had to be a better way to get this removed. I thought about drilling it out, but there is no possible way to get a conventional corded or cordless drill in there, there is no clearance. However, a right-angle drill can, and is perfect for this job if you are extra careful. Furthermore, a set of hardened left-hand drill bits will complement this job nicely.

Prior to drilling, you need to make sure that the exhaust stud is flat and not broken off at an angle. If it isn’t flat, try filing it lightly. You need to drill very straight so that you don’t veer off and drill into the head, so it would be helpful to make a small pilot hole. DO NOT put stress on the drill bit or bend the drill bit, otherwise it could break off into the stud. To help guide the drill bit, I also slipped [sacrificed] a small ¼” socket to help guide the drill bit. Start with a small drill bit and work your way larger, carefully drilling straight through the stud; if you’re lucky, the reverse drill bit will grab the stud as it’s drilling and extract itself. If this does not happen, drill as much as you can without damaging the threads in the cylinder head. Then, use an easy out and very carefully extract the exhaust stud; this will work a good portion of the time, but be prepared that it might not.
If the above does not work out or you experience difficulties (drill bit or easy-out snaps off, or drill bit veers into head), you may actually need to remove the cylinder head and determine if it can be repaired.

The moral of the story: If you’re unsure about the age of your exhaust studs, replace them before installing your manifold/headers. Secondly, when tightening the exhaust nuts, use new and proper hardware meant for high heat conditions and do not over-torque. This will almost always prevent an exhaust stud from breaking and causing you many hours of grief and/or a significant amount of money.