Sheared off bolt for muffler brace into exhaust Manifold

[Texasmark]

I have done so many bolts like this.... This one is easy. It's out in the open.

Weld a washer to the bolt. Cool the welded stud with candle wax. Just hold the candle against the cast manifold momentarily several times. Be careful not to start a fire. As the area is cooling, tap the washer for about a minute with a ball peen hammer. Weld a nut onto the washer once the bolt is cool. Again cool the area with candle wax. Again tap with a hammer. You don't need to hit hard. What you want is the heating and cooling and the vibration to loosen the rust.

Put a flat wrench on the nut and start moving the wrench back and forth firmly. You don't want the welding to break but you want to use enough force to start breaking the rust up. Once you can feel a bit of movement then you know you've won the battle. Spray liberally with WD-40 to wash the rust out of the threads and keep moving the wrench back and forth. Soon it will start moving a little more. All of a sudden your at a quarter turn. Smile!

I've also used an 3/8" air impact set at the lowest setting (1/2" is too large). Don't hammer long in one direction. As you are hammering just change the direction of rotation back and forth. It doesn't hurt an air tool to have directions changed while holding the trigger. I've never done it like this but an air chisel with a punch point in the center of the nut would also do the trick.

Several more hints. If the weld breaks just start over. I've started over up to 4 times before winning! In the highly unlikely event that the threads are galled you will still get the bolt out. It will be tough going all the way out and the threads will be ruined. You might be able to repair the threads sufficiently by running a tap through. If not just install a Heli-coil. When you install the new bolts use never seize.

Edited to add that this is not a job to rush on. Take your time. Every time the bolt heats up it expands. It can't go anywhere because of the cast iron around it. When it cools it shrinks. So even without any rotation you are still getting movement.

Excellent advice. On impact vs brute force, I go for impact hands down....doesn't have to be a dedicated tool.....a hammer on the end of a wrench will back out problems when brute force on the wrench would just strip out or break the bolt. I think the process is that the impact drives the subject beyond the "yield" point but removes the force before the subject has had time to react.

Getting frozen SS bolts out of cast aluminum outboard motor engine blocks is a real trick.

I like to use the anti-sieze you get in the little packets for spark plugs.

 

[TimberHole]

A cheap 3/8 drive butterfly impact works. Turn the air way down and rock it back and forth. Increase the air in 5 psi increments. It痴 worked for me when other things wouldn稚.