Manifolds

Are you installing a new exhaust manifold? If not, I would leave them together. Mine broke off when I had to replace the exhaust but then it doesn't matter as the new one is tapped for new bolts.
 
The exhaust manifold threaded holes are blind - meaning that they cannot be accessed from the inside. I have broken off several and I have found that the heat method is the best way, the same as used to take out head studs. With a torch, heat the bolts up and spray penetrating oil after. Try again, but be careful. If they don't budge a tad, more heat. Repeat until it loosens up enough. You will not hurt anything with the heat. Also, don't drop the assembly, they have been known to break after that.
 
Tricky to drill out the shaft of the bolts without going too deep, or going off center. The blister inside the exhaust manifold is fragile.
 
On an exhaust manifold I broke off, a friend of mine who does engines in his spare time was able to drill them out. Just takes "patience and caution." Obviously you do not want to get to that point at all.

I would say no to cutting the heads off as you don't really get any advantage from it.
 
chrs1961815 said:
On an exhaust manifold I broke off, a friend of mine who does engines in his spare time was able to drill them out. Just takes "patience and caution." Obviously you do not want to get to that point at all.

I would say no to cutting the heads off as you don't really get any advantage from it.
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I would think the advantage is the separation would allow access to the threads to allow penetration of a fluid to the threads and leave enough of the stud exposed to grip and remove.
 
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Maybe, but the penetrating fluid can penetrate very well. Don't mean to split hairs, I just do not see an advantage. The heat is the main source of success.
 
I have drilled out and threaded several in my experience. Most, in fact.

Best done using the head twisted off and then grind the stub down so it's nearly level with the exhaust manifold surface. This gives you a "true location" for the bolt.

With the extent of the bolt diameter revealed then with a sharp punch "centerpunch" what you feel is the centerline of the broken bolt. Then starting with a 1/16" drill, drill a hole until you feel it "drop" into the void below the broken piece.

Then in 1/16" increments, expand the hole until nearly the root diameter of the thread. IIRC, the bolts are 5/16 which has a root diameter of No. F drill or 0.257. The nearest fractional size is 17/64 which is 0.2656. I would drill this to 1/4" or 0.250 and try to pick out any thread you can reach. Then try for No F drill and pick out more.

If you can get a circle or two of thread clear THEN try putting a 5/16-18 tap and re-tap the hole. More than likely the tap will follow the previous threads removing only what remains of the original bolt. Finish up with a "bottoming" tap which can be made from a ground-off standard plug tap.

If you're a little off-center in your drilling, approaching the final thread root diameter "gently" will help preserve as much as you can of the original female thread. Being off center means you "clip off" one side of the thread form but enough will remain on the other side to allow full bolting. AND clipping off one side CAN make it easier to "pick-out" the remains of the bolt.

Use penetrating oil generously during this process.

In drilling process and coming up perhaps half way to the root diameter, I might try an 'easy out' simply as part of the exercise. I can't for the life of me remember the last time it worked, however. Easy-Outs are a nice marketing name, but don't describe well the heartbreak of breaking one off in the hole.

Hope this helps.

Joe K
 
Gottem out. Called an old friend the owned an muffle shop. Told me to heat up (very hot) the bolt alone and let it cool down naturally. Do it three times. Came right out. I guess third time's the charm!
 
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