I was tightening the bolt that runs through the top of the breather tube and broke it off. How the heck am I going to get that out?!?!?!?! Any ideas?
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Re: Help!!! Broke Off Bolt in Breather Tube!!
"How the heck am I going to get that out?!?!?!?"
Very carefully.
Keep in mind that the cast iron block is much softer than the broken (now work hardened) bolt. Drilling the bolt out is the usual extraction method. Then chasing the threads with a 1/4-20 tap. Not an easy task. Don't let any chips from drilling get into the engine. A 1/8" reverse drill bit could do the trick.
You may get lucky. There might be enough of the broken bolt exposed to grab with pliers, or just enough to tap on it (unscrew) using a small punch or chisel.
Worse case is taking the block to machine shop and have them drill it out on a milling machine.
Good luck,
Mark -
Re: Help!!! Broke Off Bolt in Breather Tube!!
One old trick, use a left hand drill bit. Quite often the bit will screw the bolt out. Just remember the important work, CENTER. Be sure to center your bit.Dick WhittingtonComment
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Re: Help!!! Broke Off Bolt in Breather Tube!!
With the breather out of the way, mig weld a drill (or ???) to the broken bolt and back it out.Comment
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Re: Help!!! Broke Off Bolt in Breather Tube!!
Hi Kirk:
Sorry to hear about your trouble with the breather bolt. I think you have already gotten some good advice for removing the part that is still in the block.
If it's broken off below the surface of the block, the standard approach is a well-centered drill hole that you make progressively larger until you can pick out the remainder of the bolt. The idea is to remove all of the bolt's inner shank while leaving the outer threads untouched. At some point in the process is usually becomes possible to remove the remaining pieces with a pick and some needle nose pliers.
By the way, don't throw away the old bolt, because the correct headmark for your 67 is not being reproduced (so I'm told). If you ever decide to go nuts on NCRS "correctness," you may want to go to the trouble of splicing your old bolt so that the judges will see the original bolt head.Comment
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Re: Help!!! Broke Off Bolt in Breather Tube!!
Kirk-----
In order to break this bolt, you either had a bolt that was SERIOUSLY weakened due to previous MASSIVE over-torquing OR you MASSIVELY over-torqued it. This is a GM 260-M material grade (SAE grade 2) bolt. The torque specification on it is 40-50 INCH/pounds.
Anyway, a technique that I use to remove broken bolts is to use a SHARP, HARDENED pick or awl (a dental tool will do). I lodge the tool against the area of the broken-off bolt that will allow me to turn the bolt in the counter clockwise direction and then I press the point of the tool in and turn. Keep in mind that once the bolt head breaks off, there is no longer any tension on the bolt threads, so the threads are "loose" and rather easily backed out. Of course, if the threads on the bolt or block were originally deformed, corroded, or dirty (i.e. the bolt would not turn in by hand), then this method may not work.In Appreciation of John HinckleyComment
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Re: Help!!! Broke Off Bolt in Breather Tube!!
It was a new repro bolt that comes from Corvette Central - not an original. Although I still have the old (maybe original) bolt. Maybe I should use that the next time I try this. I was only hand tightening with a standard socket wrench! Just didn't think I could push it to the point of breaking, but I guess I was wrong.Comment
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Re: Help!!! Broke Off Bolt in Breather Tube!!
Kirk------
A GM-260-M bolt (SAE grade 2) will shear at about 150 INCH/pounds of torque (about 12 FOOT/pounds). While this might not be regarded as "massive" torque, it is when you consider that the proper torque is only 40-50 INCH/pounds (about 4 FOOT/pounds). So, the point at which the bolt will shear is about 3 times the proper torque.
A lot of times, especially for low torque fasteners like these, the proper torque doesn't feel "like it's enough". Consequently, it's quite easy to break bolts like this. This is where an inch/pounds torque wrench comes in. Apply the proper torque and "let it be"; don't "second guess" the torque wrench or the torque specification.
Whether you used the original bolt or the reproduction, I don't think that it would matter as far as breaking the bolt. Either is going to shear if you exceed 150 inch/pounds. Plus, you're going to ruin the bolt and greatly weaken it well prior to reaching the shear torque.In Appreciation of John HinckleyComment
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Re: Help!!! Broke Off Bolt in Breather Tube!!
Thanks, great info. I really wasn't pulling that hard, so believe me, it was way easy to do. Still don't have it out, but I have called in the cavalry and we'll see if some expert vette guys can get it done. Piece of screw remaining certainly isn't freely moving right now, so I am assuming removal will involve a drill and backing the screw out - something that I know isn't always successful or easy. Chock another one up to the "learning curve", but at least I'm trying!!!!!Comment
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