Broken header bolt

[brewerbry]

I have drill out the stud as large as I am comfortable with doing using a hand drill - there is hardly any bolt left. It is just a gaping hole (do not remember the exact drill size) but there is just enough material left for a big easy out to bite on to. I have learned that you can drill out an easy out if it breaks - use several cobalt drill bits and a lot of patience! I gave up yesterday but will work some more tonight on this.

I think I will heat the whole thing with the propane torch and see if it loosens at all. Let's all be realistic with the torch - it is not a precise instrument and you end up heating both the both and the surrounding metal, there is no way to only heat one or the other. Regardless, I will apply heat for a couple of minutes and hopefully it breaks loose this time.

I guess if the heat and easy out do not work, I can just cut new threads in the drilled out bolt - the thread size is M8 course thread (.125) correct?

What a pain in the neck this has been!

[texomawaves]

I've had this happen and decided to let the professionals handle it... took it to a machine shop and they fixed it for $20 in only a few minutes.

[itsnotanova]

I spray penetrating lube on every exhaust bolt before I ever even attempt to loosen them. I also always use propane on the header bolts. I've had a few break and I had one were the drill bit broke trying to drill it out. I had to mig weld a puddle to the bolt and build the puddle up to where I could weld a bolt to it.

[tommy583]

Why did you take the bolts out? Were you putting new headers on? Is this the only bolt that gave you problems? I hope you are able to get it out, what a nightmare.

[jcslocum]

Originally Posted by brewerbry

I think I will heat the whole thing with the propane torch and see if it loosens at all. Let's all be realistic with the torch - it is not a precise instrument and you end up heating both the both and the surrounding metal, there is no way to only heat one or the other. Regardless, I will apply heat for a couple of minutes and hopefully it breaks loose this time.

No heat isn't precise but the ability to transfer heat is. Heating the surrounding metal of the head allow the head to expand and grow the hole. The transfer the the bolt is very slow due to the corrosion and the poor contact between the alum thread and the steel thread. The transfer takes time and give you a short time where the hole is bigger than normal allowing for loosening to happen. Even in a steel head this works well.

Be patient and good luck.