Modify exhaust to avoid extracting broken bolts

[aburke]

I have a '94 Z28 with broken exhaust bolts. On both sides, the two outer-most bolts broke off just below the surface of the head. After I removed the manifold, I noticed there's an "extra" hole located closer to the port. A search on this site showed ppl use this when they install headers.

I don't think I want to get headers. Instead, has anyone tried to drill the exhaust manifold to use the inner bolt holes? The bolt itself will clear the runner, but the bolt head won't. I'm thinking of welding a boss tall enough to clear the runner and using a long bolt. To make the boss, I would use a steel bushing, cut it to the length I need, and then cut it down the side so it sits flat against the runner.

Then, I'd just weld it all up and paint it black so it looks decent. Or, it might not need welding; It would just be a specialized, extra-long spacer. Think it could work??

Here's a diagram if it helps make more sense:

[Phil]

aburke,

Why don't you just remove the old bolt and install a new one in that hole? Did it break off flush with the block?

[MunsonGTA]

did you put the previous exhaust bolts in with loctite? if not, i'd just try an easy out and remove the broken bolts.

[aburke]

The exhaust is completely original, 140k miles. Those are the original bolts, and the ones that did come out were incredibly tight down to the last thread. It looked and felt like they did have threadlocker on there. With as much torque as I put on them, I was sure they'd snap, but they didn't.

The broken bolts are just below the surface. I didn't think I could get an angle drill in there or have much luck drilling straight. I saw a small pneumatic angle drill at Harbor Freight that might get in there. I'll have to measure it.

[93/96 f-body]

Man that sucks. I have the same problem but with the headers i was able to use the inner most hole. But i did break one that i needed. I have a milwakee 90 degree drill. Not fun. Let me know how you make out. Room sure is a problem. I snapped a drill bit off in the hole. I used a large diameter self tapper. I cut the starter end off. It's holding up. Just a temp. Fix until i pull the head and fix it.

[aburke]

Progress: I got one bolt out with the weld method. I welded an old bolt to the piece stuck in the head. I'm working on the other one, but it is not easy to reach back there.

[Kevin - Blown 95 TA]

I just went through this with a car I bought for a friend. It had 2 broken bolts in the driver's side rear #7 hole. I have an angle drill, but there was no way to get it in there and so I pulled the head. The two broken bolts came out really hard with the head out, and I was afraid the easy-out might break with one of them, but it came out alright. I can't imagine drilling them out straight or extracting them out with it in the car - although I didn't consider the weld method - don't think that would have worked for mine, anyway unless the heat loosens them up a bit.

So I pulled both heads and did a good valve job and put on new gaskets.

[aburke]

I got the 2nd bolt out by drilling. The weld method actually made it worse. Since it was broken off beneath the surface, some of the weld slag sank into the aluminum. If there was a chance of it moving before, it was certainly not going to move like this. I used a grinder to try to get to the bottom of it, but the grinder was chewing away too much of the head. I bought $80 worth of tools and drilled it. The bolt never budged, so I finally drilled it out completely and re-tapped to 3/8"-16.

I have since read that cast iron could crack after it is welded due to the varying hardness of the weld metal and cast iron. So no exhaust manifold welding without special welding materials.

All of this to save "time" removing the heads. And after I'm all done, a head gasket will probably blow, and I'll be having the heads re-done anyway.

[Kevin - Blown 95 TA]

I used to weld some cast iron - I would pre-heat it up with a torch and use a nickel rod and that seemed to work. If you do it wrong, it will crack.

[Phil]

Some good points with respect to using welding to remove studs. I suppose I should have been more emphatic when I suggested it, but I consider welding is really an act of desperation. I would try everything else first (with the exception of easy-outs since I have never had any luck with them.)

[Phil]

Oops! I am stepping out of line here. I didn't suggest welding in this thread. I had suggested it to someone on another forum. Sorry about that.

[aburke]

Last one is drilled out. I'm done! I'm going with grade-8 studs and stainless nuts w/ lockwashers. Is this okay?