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Exhaust manifold problems

John W.L.

I don't know if this is the place to ask a repair type question,but here goes- When I removed the exh. manifold on my 15.0 JC to braze a rusted out hole in it, 3 of the studs broke off. I have tried all the methods I normally do on other things ( drill hole and use a EZ out) but I can't get it to budge. I have taken my smallest heat tip on my ox./acc. torch and heated it too. ( I did get a hole drilled in it first before heating) I am worried about getting it too hot because always in the past the broken stud was not in aluminum such as my cyl. head is. Does anyone have any ideas to get it out without ruining the head? (note: The stud is flush with the alum. piece it is screwed into. John


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Well, you found out wat easy-outs are good for, not much. Actually, if you twist a bolt off when installing it the easy-out works pretty well.

To your problem. Center punch the broken bold as close to the center as you can. Start with a small drill and drill all the way through the bolt. There should be a pocket at the bottom of the bolt. Increase the drill size a step or two at a time and drill again. Check the tap chart and see what the drill size for the threads is and don't go bigger than that. Once you get close you should be able to start picking the threads out. If you are a little off center you can tap on the wide side with a punch and work it loose. After the bits are out run a tap into the hole to clean up the threads.

If you just can't get it out without mangling the threads you can install a Heli-coil.

Sometimes you can sit a nut over the broken off bit and weld down inside the nut. Then you can turn it out with a wrench. I haven't had much luck doing that myself.



Just a thought that might work for you.

I had 6 head bolts twisted off 3/8 above the block surface, 4
cyl. Kohler cast iron block. I asked my machinest friend about welding a washer then a nut on top of the washer on the stud. He said I have had better results with my tig welder,if you are in aluminum and level with the surface,it might not be easy. Ask the tig welder about this, it is so easy to build with the tig and not mess up the edges of the hole. After welding and getting it high enough ( 3/8 " ) to get vicegrips on it. The hot stud will heat the area around the stud and expand it a little. After a few seconds, cool the stud as quick as you can with air or water ( he used water ) This will shrink the stud. Water can cause the stud to harden and be too brittle,in my case 1 stud did that,he got it on next try. Threads were perfect and I was happy. Tig welding is kinda slow and the heat is easy to control. Hope you have good luck,I know how it feels. Arthur :)

Geoff Morgan

This is a very good place to post this question. Concerning broken and stubborn studs (and bolts) I've had great results and disasters on the same head, block, machine part. Most important: DO NOT HEAT ALUMINUM. Iron or steel, of course, react very well to a nice yellow/red heat. With aluminum; if you are lucky, even low heat will result in the steel threaded component just "pulling" the threads right out of the head; if you are not (recall that Murphy is usually present), the aluminum material around the threads will crack and/or "fall out" leaving a job that will require TIG welding to remediate.

The best technique in my opinion is to rig something to center a drill over the axis of the fastener, such as a nut with a another bolt sawed off in it and center drilled or a little sleeve thingy with a center hole. Yes, these things are best made in a lathe, even a little 6" or model lathe, but a drill press will work if you have a good vise, some skill, and a lot of patience. Use a small drill, but not too small, say a 1/8" to start. Once you have a good hole down the center axis of the offending fastener you can move to a larger diameter drill so as to use the largest eazi-out possible. With a battery drill you can opt for a left handed drill bit, I've had a lefty "hang" and the stud backed out!! Don't break that eazi-out; give up if things don't move right away and just drill out the fastener preferably with the correct tap drill size for the offending threads and reclaim them with a tap or helicoil new threads. If there is not enough of the fastener protruding to put a nut or a sleeve over, try to use a "transfer" punch to center punch a concentric spot; make up a drill fixture so as to hold the drill in line with the axis. Of course, this is all assuming that you cannot square the whole assembly under the quill of a Bridgeport vertical mill!

Some eazi-outs marketed today are too soft. Some have too much taper. I have had good results with both the traditional left twist taper and the new drill/cone integral units. I think that over all the longer more gentle taper type would be my first choice on a stud in aluminum. I've had some of the new short left integral drill out units shatter, hand held is not too good with them and they don't lend themselves to the sleeve guide. You have to use them after you get the center drilled.

This describes a lot of work and trouble, but the results can bring pride and the alternative of failure will make you unhappy to say the least and cost a lot more than the time invested on the side of care. I have been working on "junk" and components that were abandoned by others as unrepairable for nearly 50 years now, and I have had a few fasteners that whipped me, but overall the previous scheme has worked the best for aluminum. Good Luck, Be Careful, Work Safely, Geoff

Stephen Girouard

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if you can drill the old bolt out straightleaving the rusted threads in the aluminum then chasin with a tap , or pic out the old threads,that works, or take off the heads and end mill it out , if you do damage threads sometimes enough casting exist to go to next size larger stud