Broken valve cover bolt:(

[pontiacpower]

hello fellers.
so I’m putting a 400p together for my 71 Lemans and somehow I managed to snap a valve cover bolt off in the head. I think the depth of the threads in the block was a little more shallow then the others so I think the bolt is bottomed out. I used drill bits to run a hole in the bolt and then tried easy outs with no success. Then I tried left handed drill bits and that didn’t work. Finally I tried one of these broken stud removers from Lowe’s that looks like a torx bit that’s twisted so it grabs the same way an easy out would. Naturally I broke off the tip of that in this stainless steel bolt. Now I’m pissed. Then I asked a guy at work about my problem and he said to use torches to heat the steel up and then hit it with oxygen to blow out the steel from the cast iron head. Any truth to this? No torches here but I’m sure I have friends who do.

So here I am putting an engine together for the first time and I’m hung up on a valve cover bolt of all things. Is there anything else I can try? And now I’m nervous about getting steel shards (from drilling) into the oiling system. What can I do to clean up all the small pieces of steel? Tried a magnet but not as effective because the valve train is in the way.

thanks for any help in advance

[Loren]

Jeez don't touch that thing with a torch/oxy. There is a metal removing device that works with an arc welder but would not be precise enough.

The last resort is to find an EDM (electrical-discharge-machining) shop near you (most industrial areas have one) that advertises broken bolt removal and have them take it out with a die sinker. You'll probably have to take the head off and bring them that but ask about it first. See for example: http://brokentap.com/

[AndyB]

Is that an iron head? If it's aluminum, you could chemically remove the broken stuff. If it's iron...notsomuch.

However, the unfortunate news is that your best bet is to start by taking the head off. Set it up on a drill press so that it's dead level (so you can drill the hole properly). A carbide burr in the drill chuck is the first round, and by pecking away you may be able to get everything out. The second best solution is to grind it out, using a diamond drill. Eventually, you'll need to helicoil or otherwise repair that hole, but that's not a huge deal. You will definitely want to measure how deep the hole originally went so that you don't go too deep, also--it's easy to overdo things once you start making progress!

EDM is definitely the right answer, but it's totally possible for a home guy to fix this sort of thing. I'm dead serious when I say that it's worth the trouble to get it off the motor and into a fixture where you can ensure that you're drilling straight though. It's just shy of impossible to do it by hand, though you'll read occasional stories where someone managed it, there's probably 50 where they just made things worse.

[squirrel]

...and don't use stainless bolts, use steel bolts. Stainless bolts might be useful on a boat, but are not really what you want on a car, for pretty much anything.

[anotheridiot]

What is left after you used the lefty drill? best way I think is to button hole weld a nut on the broken bolt before it gets mangled too much. There is still pretty good room around it to enlarge the hole after. Dont know if you can go to 5/16 but bite the bullet and use a 7mm.

As far as metal shards, it helps to grease the drill bit to grab the chips as long as you are drilling slow enough.

[Deaf Bob]

A big speaker magnet helps collect shards.. Put one nearby..

[pontiacpower]

Thanks for the replies so far guys. I kept a circle magnet under the broken bolt so gravity would help that steel find the magnet. There is a shop nearby that does edm. Is this the first choice? I borrowed a hoist to move the block to my new place so I can load it back up in the truck and take it to the shop before I return the hoist. What’s the turnaround on an edm job?
If this isn’t realistic then I guess it’s back to drilling.

[pontiacpower]

[Loren]

Well, EDM is the last choice not the first, but it sounds like maybe that's where you're at. The shop may need to immerse the whole head in fluid because of the way EDM works; cool water alternating with little lightning-hot sparks disintegrate the metal. So, you wouldn't be worried about moving the whole engine, rather just take the head off so they can dunk it in their tank..

The last time I had a broken tap EDM'd out of a piece of metal is was like $50 and a few days. Ouch, but what else are you gonna do sometimes. That sucker would just not come out any other way, and I didn't want to ruin my part, a steel die set with a lot of time into it.

You've mentioned you may be new at this, know that this-type thing is a pain and you aren't going to find it easy to understand why you gotta take stuff all back apart over one little problem, but that's the way it goes sometimes with old cars or really, machinery of any type. Dealing with this small problem which is actually a big problem will separate you as a doer and a successful engine builder from the many many unsuccessful dreamers. You know that you can never have peace with a motor that's missing that fastener so make it right and my hat's off to you for having the patience to get it right, if that's what you do.

Finally, if you go EDM, make that shop explain to you what they're doing and maybe show you the process in exchange for you trusting them with your parts and giving them your money. Might be informative.

[malc]

The last time I had this problem was on a Qjet carb., one of those long ones.
By a miracle I got a hole drilled into the bolt...not very deep and a square punch pushed into it broke it free....
Next problem.....I did'nt have a spare bolt.

[JamesMayberryIII]

you try wicking wax down the threads?? works everytime. unless, you cross threaded, or put the wrong pitch thread in the bolt hole.

[cstmwgn]

From his description it sounded like the bolt bottomed out in the hole and then wrung off. IF this is in fact what happened then the bolt is tightened into the hole pretty firmly and most likely won't be receptive to the types of removal methods used for rusted / frozen broken bolts.

[anotheridiot]

I thought EDM was just used with unlike metals and when it is a super hard tap. He just has to get a good ole cobalt #7 drill and just retap the hole. If the threads dont get found then upside it to the 7mm or 5/16.

[malc]

I use studs where ever I can...even valve covers,
they hold the gasket and the cover plops right on.

[chevybuytroy]

I know I deal with a lot of broken exhaust bolts. The best drill bits I’ve ever bought was off a cornwell truck. I heat them with a torch then the drill bit pulls them out. All else fails weld a nut to the top and try turning it out