Best way to remove broken bolts out of exhaust manifold?

[White70C20]

I am rebuilding the engine out of my blue '70 C20. It is a 250 inline 6.
There was a little metal cover with a spring inside and a rod sticking out of it bolted to the exhaust manifold (what is this little thing?). When I removed it, I noticed that one bolt was already sheared off and when I removed the other bolt, it sheared off as well.
These are small bolts, and I was wondering what some of you more experienced guys would suggest I do to remove these bolts (they broke flush with the surface of the manifold)?

The engine is coming along really well, I've installed several new parts to help ensure that this engine lasts a long time. Thanks!!!

[swamp rat]

Well if it was a sbc 350 with an automatic choke and it was sticking out of the intake manifold I'd say it was the bi-metalic spring that actuates the choke on a factory Rochester carb.

But being new to the 250 i haven't got an answer for you.

Per the small bolts your going to have to drill them out, use a bit smaller then the inside diameter of the thread pitch of the bolt, If possible try and get a center punch on the screw to help start the drill, try and stay centered and drill straight, then use a small easy out.

Another tip is to try and locate a left handed drill bit, sometimes one can get lucky and have the remaining screw actually back out while drilling.. But if its rusted into a manifold don't know if that would be successful, but use a lot of penetrating lube on it for a couple days and stranger things have happened...

[SS Tim]

Must be talking about the choke coil.
This right out of the service manual.

[70shortstep]

That is the choke pull off. I just had the same thing happen to me. I drilled a hole right next to the broken screw and put in a self tapping screw. Worked perfectly.

[GRX]

Blind hole or all the way through? Drill a small hole down the center of the broken bolt and blow it out with a Torch.

[motorcritter]

A proper sized drill and extractor should do the job. Soak well with Kroil, after drilling the hole. If possible, hit it with a torch before drilling and soaking. Worst case- drill the remains out and retap or Heli-Coil. Good luck and happy wrenching!

[imjeff]

Soak it for a few days with a good penetrating oil. Take a center punch and smack it every time you think about it (penetrating oil, smack, repeat). Then try a left hand drill bit and an ez out. If the threads are tatered you can heli-coil it. As an alternative you could upgrade to an electric or even a manual choke, depending on the carb.

Jeff

[brad_man_72]

Weld a nut to the broken bolt.

[White70C20]

Thanks guys. I was suspecting that's what I was going to have to do. 70shortstep, that sounds like an interesting option.

[jdw]

Center punch it, drill it out, use a reverse thread tap in the hole and insert a reverse thread high grade bolt. When the reverse thread bolt tightens in the hole you made in the old bolt it will turn the old bolt out. Make sense? Of course, that's gonna depend on the width of the old bolt, but it works.

[GRX]

Done this hundreds of times for customers over the years. Cast iron has a high melting temp. Use that. If you had the 250 exhaust manifold in my shop I'd drill & blow those broken bolts out with a torch in no time. And if the holes are blind I'd drill small holes in the side of the manifold for the molten metal to escape. Most times you can melt out the steel without damaging the cast iron threads at all.