Oxy / acetylene to remove stuck exhaust bolts

[Atlas]

I have two exhaust bolts that I've spent some time on and can't seem to free them, out of 8 , 5 loosened easy , 1 broke and two are stuck and I don't want to break them too. The one that's broken has a 1/4" out of the head that I may be able to work on when the exhaust is off. I've tried everything that has been suggested on other threads , different types of penetrating oils , ATF/acetone , tapping with a hammer , nothing so far. I've noticed questions on oxy/acetylene but never seen an answer to whether it's to hot or not. Can the heads handle the heat? I don't know if anyone has had any luck with this or not. Any knowledge or experience on this would be great, thanks

[81GS750]

If your not very careful, you will melt the aluminum. Have you tried welding a nut or bolt to the broken bolt? If you don't have access to a welder, like me, find some cobalt reverse drill bits. Grind the broken bolts flat and drill baby drill! I did that in combination with heat from a MAPP gas torch and PB Blast. IF your lucky, your just dealing with stock bolts that are fairly soft. I had to deal with hardened header bolts

[Atlas]

Thanks , yes they are just stock bolts. I haven't even tried to do anything with the broken one yet. Seems like there's no definite method for removal, but drilling is one that seems fairly successful(no other choice if all else fails). I will just try welding the head back on first if that breaks maybe just clamping down hard with a vise grip with the back forth technique and then go to drilling. But first I want to deal with the two that aren't broken but are really stuck.

[Hammered]

How close to being flush are these bolts? If you can cut a cross in them with a rotary tool, an impact driver would be a really good place to start. Hand that you tap with a hammer or the electric type both work fine. A nice large #3 Phillips or Asian phillips would be best. Soak the bolt to hell and back several times with your favorite penetrating oil. I prefer Kroil from the store bought types. Set the impact to the lightest setting and work your way up til it comes loose if you have an electric or tap lightly if you have a hammer style one. You can also try something like Freeze-off. Its a penetrating oil chills the broken/froze bolt, instead of heating the area around the bolt. These methods will also work if you can weld a nut the broken bolt.

[Nessism]

For the existing, but stuck, screws, I suggest getting them good and hot a few times followed by repeated spraying with penetrating oil. Try working them both in and out, back and forth, but never forcing them. The idea is to get them to move a little. If you can get them unstuck, even just a little, you have a very good chance to get them all the way out without breaking them if you take your time and continue to "work" them.

[1980GS1000E]

After that is all done you can replace them with studs.

[Atlas]

Thanks everyone , only one is broken, and I'll leave that one till I get the exhaust off , I'll try heating the bolts , I've never done that yet , usually it's where the bolt goes into that needs to be heated , but no one is advising me to do that so I won't. I guess the heads can't take the heat from oxy/acety.

I think maybe with some patience and a good tight hold with vise grips may get the broken one out , there is definitely enough to grab on to. But first I'll try to weld the head back on the bolt and try that.

[Jason the terminator]

Use a oxygen map or just map torch. If using oxy map get one with a jewelers tip, can get at any hardware for around $40. Heat just the head of the bolt. You should be able to get the bolt head red hot with out damaging the cylinder head. Aluminum melts at 1200f which with on of the two options I gave you you would be hard pressed to reach. If it would make you feel more comfortable get some heat sink and put it around the head of the bolt. You should also be able to get the broken one out by heating with a torch and a pair of vise grips. Should be able to get them out fairly easy and replace them with stainless bolts with some anti seize and never worry about them again.

[Atlas]

Thanks Jason, good to know , I'll maybe give that a try. I also could definitely get the bolt to that heat with a oxy/acety tip. It's pretty easy to control , I can just use a smaller tip and back off on the oxygen a bit , that's what makes it hot.