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  #1  
Old 05-04-2001, 01:06 AM
swinger340 swinger340 is offline
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I had to have to bolt holes in the back of my 340 block Heli-coiled because I was stupid and twisted off two grade 5 bolts when attaching it to an engine stand. Is this the only way to fix it when the bolt broke off flush in the whole? I learned my lesson young, measure the depth of the hole before cranking a bolt down.
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  #2  
Old 05-04-2001, 01:44 AM
fat bastard fat bastard is offline
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Sometimes you can save a thread, but generally speaking a heli-coil is stronger than the material it goes in to.
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  #3  
Old 05-04-2001, 02:55 AM
70Chall383 70Chall383 is offline
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If the bolt snapped but the threads are alright you can sometimes get it out with an "easy out" if that wont get it out you can either heli-coil it or drill it larger and tap it out to the next size. There are probably other ways that i am not aware of.
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  #4  
Old 05-04-2001, 05:46 AM
DAVE JONES DAVE JONES is offline
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The threads in your block were still good and hopefully they did at least give it at least a quick try before they helicoiled them. They possibly tried to do this but couldnt. Bolts usually break for one of 3 reasons. The first usually occurs during the removal of an old bolt that has rust in the threads and is locked up. The second is when putting in a bolt and torquing it down, it snaps......But.....its not because it bottomed out in the treads. It was either a weak bolt or it was just overtightened. In the first 2 situations, these usually can be removed easier than the situation that you fell into. The 3rd situation is what occured with you. If a bolt breaks during torquing due to bottoming out in a threaded hole, then twisted till it breaks off, It can be extremely hard to impossible to remove. What occured here is that you actually didnt bottom out the bolt on the bottom of the hole, but bottomed the end of the bolt on the end of the threads. The end of the tapped hole has threads that taper down in size and your bolt had so much pressure applied to this, The end of your bolt was acting as a Form Tap and displacing (swedging) material down at the bottom. This causes a serious "line to line" fit. When this situation happens, then it usually takes a very skilled machinist to get it out without damaging the threads and costs skyrocket because of the time it takes to get them out or even try to get them out. In your situation, it probably was the most cost effective solution for you and the helicoiled threads that you have now are stronger that what was there so you can rest at ease .......Dave
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  #5  
Old 05-05-2001, 12:04 AM
Karl43 Karl43 is offline
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Heli-coils are strong. I've heard of people using them on head bolts. They are also recommended in the Chrysler service manual.

To remove a bolt that is broken flush or underflush with the block, I have found that Snap-on has some nice removal kits. One kit has a collars of different diameters that can be used on underflush (lower than the edge of block). I like the collars/sleeves to center the drill to drill a hole in the block. I do not care for the "easy outs" in this kit as they are round with four "barbs" running the full length. The other Snap-on kit is a set of three to four "easy outs" that have four corners and a left hand pitch (because you are trying to back out the bolt). This is my favorite easy out to use because it is easier to remove/beat off what is left of the old screw after removed. The ones with the strait barbs are not as easy to remove the old screw. The last "easy out" set from Snap-on is small left hand easy outs with hex heads on them. The center drill sleeves are useful with these also. Believe me it is much cheaper in the long run to have a good set of easy outs - they will pay for themselves.

If a broken bolt is stuck into the hole one of the best ways to "break it loose" is with heat. Nothing like a good propane torch to heat up the bolt and block after center drilling, but prior to installing the "easy out" of your preference. Once the old bolt is good and hot, drive in the "easy out" with a hammer and use a wrench to unscrew the bolt. This is worth trying before taking to a "professional". Can save you time and money. Note: Do not heat hardened parts or springs as the heat can damage the part (ie. torsion bars, leaf springs, arounnd gas tanks etc.). Engine parts and blocks are safe to heat to remove stuck bolts.
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  #6  
Old 05-05-2001, 10:25 AM
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DartByU DartByU is offline
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Heli-coils are stronger than the original threads, and as a machinist who has taken out lots of broken screws I will tell you to stay away from easy-outs, sometimes they work good, but on a screw broken off like yours is the easy-out will probably break off in the screw and then it will be VERY hard to do anything with it because the easy-out is harder than ANY drill bit and you will never get it drilled out. One trick we use in our shop is to have a good welder tig weld material to the top of the broken screw and then we clamp vice-grips on the welded material and it will usually come out, if that does not work then we put the block in a mill and drill out the old screw and most times it will not have to be heli-coiled. Good luck!!
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Old 05-06-2001, 04:58 AM
Robert Mcdougall Robert Mcdougall is offline
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One alternative to the heli-coil I've seen is a threaded bush insert, seems to work ok. Simply drill and tap to a larger size, to suit the bush.
Personally I dislike using easy outs that use a left hand taper thread, as the harder you turn the more it digs in and spreads the bolt into the thread.
In Engineering there are a zillion ways to get things done and equal number of gadgets to do them. You make the choice to suit yourself
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  #8  
Old 05-06-2001, 09:31 AM
wrenchturner wrenchturner is offline
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I personally don't care for Helicoil,as I have seen them come out with the bolt when it is removed later.This happens when the Helicoil is not properly installed.
I prefer to use a Keensert,these thread in an oversized hole and then pins are driven in,or a solid plug then drill and retap.
There is 100(or more)ways to get a broken bolt out,I have used easyouts successfully and I have broken them off,you do not want to break one off.Try center punching then drill progressivley bigger holes until only the threads of the bolt are left in the hole then try to pick them out.This takes a gret deal of patients and time,but it is worth it as you preserve the original threads.
Good Luck!!
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  #9  
Old 05-06-2001, 11:53 AM
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ehostler ehostler is offline
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I've had a few helocoils, due to breaking exhaust bolts. They just torched the bolt out and then retapped the hole and put the helicoil in. Took them less than five minutes. The fix was very strong. I never did pull out the helicoil, when taking the bolts out, later.
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