Broke bolt off in crank, now what?
01-30-2006, 04:19 AM
#42
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Originally Posted by 2xLS1
Because even though this happenes over and over and crank threads continue to get stripped, people still install pulleys with a bolt instead of a piece of all-thread, washers and a nut. Sucks that it happened, but that's why.
01-30-2006, 04:38 AM
#43
Don't blame the pulley for this problem. When you felt the torque start to increase dramatically is the time when you STOP and ask your question on LS1 Tech. Don't wait until you break the bolt off to ask "What do I do now"? It's hard to understand how the bolt came part way out then decided to become difficult. You've already had some good suggestions like drilling the bolt out with progressively larger and larger bits. Do you have the clearance you need to get a drill motor in there? You may need to use a right angle drill motor. You might try drilling it out enough to get the biggest screw extractor that will fit in there. Then you turn the piece that's left in there further BACK IN because the threads that it is trying to get past must be damaged keeping the bolt from coming all the way out. You then run a BOTTOM tap in there to dress the threads (don't use a taper tap). Once the threads are free of burrs you can reinstall the screw extractor and remove the offending member. The pulley is an interference fit. That's what holds the pulley in place, not the bolt. The bolt is there for safety reasons. You can't chance running a engine at 6K without a bolt in there to make sure the pulley doesn't become schrapnel in the event it were to come off because there was no bolt there to keep it from walking off of the crank snout. The pulley only drives the A/C, water pump, PS pump and alt. so it uses interference fit. It you were spinning a blower off of that pulley you'd probably want a key and keyway on the crank.
01-30-2006, 08:21 AM
#44
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Originally Posted by eallanboggs
Don't blame the pulley for this problem. When you felt the torque start to increase dramatically is the time when you STOP and ask your question on LS1 Tech. Don't wait until you break the bolt off to ask "What do I do now"? It's hard to understand how the bolt came part way out then decided to become difficult. You've already had some good suggestions like drilling the bolt out with progressively larger and larger bits. Do you have the clearance you need to get a drill motor in there? You may need to use a right angle drill motor. You might try drilling it out enough to get the biggest screw extractor that will fit in there. Then you turn the piece that's left in there further BACK IN because the threads that it is trying to get past must be damaged keeping the bolt from coming all the way out. You then run a BOTTOM tap in there to dress the threads (don't use a taper tap). Once the threads are free of burrs you can reinstall the screw extractor and remove the offending member. The pulley is an interference fit. That's what holds the pulley in place, not the bolt. The bolt is there for safety reasons. You can't chance running a engine at 6K without a bolt in there to make sure the pulley doesn't become schrapnel in the event it were to come off because there was no bolt there to keep it from walking off of the crank snout. The pulley only drives the A/C, water pump, PS pump and alt. so it uses interference fit. It you were spinning a blower off of that pulley you'd probably want a key and keyway on the crank.
So far what I think I'm going to do is use a drill thats just smaller than the threads and try to drill the core of the bolt out, leaving just a shell. I'm then going to try and find a way to get this shell out.
If that doesn't work, I'll completely drill the thread shell out, taking out the crank threads too. I compared the broken bolt to the backup bolt I bought and it appears .35" is all that's broken off. If I do end up taking this route, I'm going to clean everything up then attempt to thread a new bolt in there using the existing threads minus the .35".
If that doesn't work I'll retap that .35" and hope the threads line up with the old ones. If that doesn't work I'll drill the entire section out one size larger and tap it for a larger bolt. If that doesn't work I'll donate plasma on a regular basis until I have enough for a forged shortblock.
Wish me luck and or give me some advice on this plan of attack. I was gone all weekend, but I'm going to at least get the radiator and fans out of the way by today.
01-30-2006, 11:45 AM
#46
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Originally Posted by vettenuts
Do you have a centering tool of any kind? I would drill progressly larger holes until you are just at the thread ID of the original threads then try to pick the old one out.
Good luck.
Good luck.
01-30-2006, 12:46 PM
#49
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I got my larger bolt out with no problems, but I'm thinking that "larger bolts" are ordered from various places and shops. Metal quality on some could have been very poor, and prone to breaking. I guess you got bad luck....
I hope everything works fine for you. I know it's a pain to drill the bolts. My friend had to do it on his turbo flange bolt, which seized.
A good advice to you: Use high quality drill bits, otherwise you'll go through 30-40 other drill bits without even making a notch. You might think that 50 regular ones is gonna do, but you're wrong...Use the Titanium, or Tungsten plated ones, that are made for drilling metals...
Good Luck !
I hope everything works fine for you. I know it's a pain to drill the bolts. My friend had to do it on his turbo flange bolt, which seized.
A good advice to you: Use high quality drill bits, otherwise you'll go through 30-40 other drill bits without even making a notch. You might think that 50 regular ones is gonna do, but you're wrong...Use the Titanium, or Tungsten plated ones, that are made for drilling metals...
Good Luck !
01-31-2006, 01:36 AM
#53
You might try using a sleeve as a guide for your drill bit. You do have an old coffee can full of assorted sleeves up on the shelf don't you? The OD of the sleeve has to be such that it just fits inside the bolt hole being held in place by the threads in the crank and the drill bit must fit snugly inside of the sleeve. If the face of the bolt is irregular where it broke off you may need to grind the center of the broken portion of the bolt flat so that the drill bit doesn't try to walk as you begin drilling. You can try using a die grinder or a dremmel tool for this. Once you get a pilot hole drilled using the sleeve you can finish it off using a bit slightly smaller than the threads. As that point you should be able to dig out the remaining material since it is only 0.35" long.
03-07-2006, 09:51 AM
#54
This just happened on my buddies car last night. 
Same deal, longer bolt seized up and broke off on the way out. Does anybody know the ID of the crank snout before the threads start? Im going to turn down a collared sleeve on a lathe so that I can start the first drill bit true.
I cant tell you how many times ive sucessfully used the longer bolt method. I cant figure out what the hell happened that seized it up. Didnt crossthread, didnt bottom out...
Same deal, longer bolt seized up and broke off on the way out. Does anybody know the ID of the crank snout before the threads start? Im going to turn down a collared sleeve on a lathe so that I can start the first drill bit true.I cant tell you how many times ive sucessfully used the longer bolt method. I cant figure out what the hell happened that seized it up. Didnt crossthread, didnt bottom out...
Last edited by GuitsBoy; 03-07-2006 at 10:46 AM.
