Mikelly Posted January 2, 2005 Share Posted January 2, 2005 Any of you guys know if it is possible to repair or replace the threads in the end of a crank shaft? Had something happen today I've never experienced before... Installing the balancer for the FOURTH time, the bolt got hung 3/4 of the way in... Wouldn't come out, wouldn't go further... I heated it, and tried to gracefully back it out, and after all else failed, I hit it with the impact and removed it... completely trashed the bolt and the inside of the snout of the crank... I feel sick... People wonder why every year at this time I contemplate unloading this project... This balancer has caused me more problems than it is worth... I'll never buy another Fluidamper...Not worth the friggin' metal it is made of... SFI or not...I have heated it, lubed the crank snout, lubed the inside of the balancer, hit it with steel wool, sand paper, and it still would not go on without SIGNIFICANT force, and even then not all the way on... Mike Quote Link to comment Share on other sites More sharing options...
DaleMX Posted January 2, 2005 Share Posted January 2, 2005 Mike, the crank snout should be soft enough to drill out and re-tap to a larger size. Larger is stronger! If you went the helicoil route you would have to re-tap anyway so why not just go up a size. Your just trying to hold the balancer on. Personally I use a threaded rod mounted all the way into the crank, then use a strong nut to push the balancer on. Then remove the threaded rod and locktite the bolt on. Quote Link to comment Share on other sites More sharing options...
Guest Phil1934 Posted January 2, 2005 Share Posted January 2, 2005 Drill out the bad threads and get a longer bolt. You should have good threads deeper. Quote Link to comment Share on other sites More sharing options...
dr_hunt Posted January 2, 2005 Share Posted January 2, 2005 I'm assuming that this is a new balancer that was never installed?... Or, is the crank new?... Either way, what does the crank snout measure and what does the inside of the balancer measure? There are threads in the crank that don't normally get used, but... Well, I hope you don't end up having to send it to a machine shop to get it redrilled deeper or larger, both can be done. Quote Link to comment Share on other sites More sharing options...
Jolane Posted January 2, 2005 Share Posted January 2, 2005 Mikelly, I had the same trouble with my Fluidamper also on my 383. I put it on a Scat crankshaft, and it was very tight. At the time I put it on though, I did not have my install tool, and instead tried to pull it on with the ARP bolt. I always thought it was so hard because I did not have the tool, but now I am starting to wonder... Anyways, if it happened to me, I would look at using a Keensert instead of a helicoil. A helicoil should work fine for you, but I like Keenserts more. They are basically an adapter, used like a Helicoil, but solid instead. They lock into place by driving two (or more) pins alongside the insert. The problem with Helicoils is thread locker. If you plan to locktite the bolt in place, once you remove it you have a good chance of pulling the helicoil out also. The problem though with Keenserts is that they require a larger tapped hole to work. Don't use a heavy one (as in heavy duty, thicker), and that should help minimize how much material you remove from the crank. Good Luck, I hope this helps... Joshua Quote Link to comment Share on other sites More sharing options...
datsunlover Posted January 2, 2005 Share Posted January 2, 2005 Sounds like maybe a tiny bit of metal or maybe dirt (somehow?) caused it to 'pick up' and that's why it stuck.. OR.. it was actually to long of a bolt and bottomed out? After bottomng out, even a little presure is enough to pull threads if the 'fit' is tight. (IE;tight tolerances between threads) The other (less likely) thing would be that the bolt was the wrong thread for the hole... but I assume not because you already had it threaded it a few times right? As for fixing, it is most likely posible to chase the threads to clean them up.. just use lots of taping fluid, and go slow with the tap. Quote Link to comment Share on other sites More sharing options...
Mikelly Posted January 2, 2005 Author Share Posted January 2, 2005 The crank is a brand new Scat9000 internal balance and the balancer was used, bought here from a member, but in good shape. I'll have to take some measurements on th and see what they come to. I don't think this thing should be as tight as it is... I've broken TWO install tools and now a ARP bolt. The threads appear to be trashed, but I'll sort out finding a tap and see if I can clean the threads out and salvage what is in there... I'm not gonna re-use this damper... and it will likely go in the trash... Mike Quote Link to comment Share on other sites More sharing options...
Guest Magnum Rockwilder Posted January 2, 2005 Share Posted January 2, 2005 Take a dremel and clean the damper up a bit, and use some high temp grease on the back of it. ...and as stated above, your best choice is to drill out the damaged threads and hope there are some good threads in there. If not you can go ahead and tap it over or install a Keensert. Quote Link to comment Share on other sites More sharing options...
Ferd/289 Posted January 3, 2005 Share Posted January 3, 2005 For the next time.. ( you may know this already, if so I apologize) it helps when attaching bolts to hard metal like cranks and cast iron block threads, to screw in 1 or 2 turns, then out 1 or 2 turns, then again in progressing 1 or 2 and out, etc. I have always done this since a machinist told me this years ago. Hope this helps..good luck. Ferd Quote Link to comment Share on other sites More sharing options...
datsunlover Posted January 3, 2005 Share Posted January 3, 2005 Yup. It actually will 'clear' the threads as you back off a bit, and then turn the bolt in. Like taping; turn a few turns in, and back off half turn or so to 'break the chip' and so on and so on. With tight threads/close fits, the threads can actually try to cut as they thread in, like 'cross threading a bolt' only not to that extreme. I don't know for sure in this application, but some threads are actually an 'interfearance fit' and are tight ALL the way in, right from the start... I actually find that trick quite helpfull when removing rusted bolts as the rust will bind and stick in the threads. When you tighten it back in slightly, you clear the rust and can then unthread the bolt more each time you do this. I just removed the nuts/bolts from my z's exhast maifold yesterday by doing this... well, two of them. I forgot and snaped the first one off after cracking it loose and going 'hog wild' thinking it would spin off... Quote Link to comment Share on other sites More sharing options...
zeeboost Posted January 3, 2005 Share Posted January 3, 2005 Yup, same thing happened to my crankshaft -- I too broke two harmonic balancer installer tools (though they were a crappy design) and ruined the threads inside the crankshaft attempting to instal the damper with the bolt. I took it to my machinist and had him put an insert in it, and then the INSERT CAME OUT when I torqued the bolt to about 35 ft/lbs. So, I took it back to him, and he double-inserted it, and was successfully able to torque it to 65 ft/lbs (I think that's how much). But, I would just suggest to drill out the ruined threads and re-tap the crank for a larger bolt. Good luck Quote Link to comment Share on other sites More sharing options...
Guest 77vegasz Posted January 3, 2005 Share Posted January 3, 2005 To repair it to the original threads, use a heavy wall Keen-Sert. They are available through a local fastener company, or McMaster-Carr. A Keen-Sert is a high grade steel insert that is threaded inside and out. You will drill and tap to a larger size to fit the OD of the Keen-Sert. You screw it in untill flush, then it has four metal wedges that drive into the shaft and the insert on the od to prevent it from turning. I work at a machinery fabrication facility, and this type of thread repair is the preferred method in industry for heavy duty applications. It is far superior to a Helicoil, and thre grade of steel in the insert is far superior to the cast iron in your crank. Jon Quote Link to comment Share on other sites More sharing options...
BillZ260 Posted January 4, 2005 Share Posted January 4, 2005 Just wanted to clarify something, there are NO "interference" fit threads. There ARE thread "FIT" classes, ie: Class 1-4, 1 being Loose, 2 Free, 3 Med, 4 Close but not tight. The class 4 thread movment between the nut and bolt feels almost like a wheel bearing. You can't really spin it, but it easily turns. Any threads that are difficult to tighten are either cheaply mass produced or the wrong size. Mike sounds like the two materials work hardended under the strain of the bolt trying to pull the dampner on and they welded, or a thread gave under the stress. As for a fix, dunno much about helicoils or the Keenserts, have never used either. I would try cleaning the threads with a tap and a LOT of tap oil and see how much of the actual threaded area in the crank is dammaged after you clean, If it is jut the top of 1 or less complete thread I would say you are ok. Most of my back ground on this is from being a machinist for ~7 odd years and breaking taps not bolts but it is all in the same boat, trying to save what your working on. Oh and here is some helpful info on nuts, bolts and threads...http://www.gizmology.net/nutsbolts.htm Quote Link to comment Share on other sites More sharing options...
Mikelly Posted January 4, 2005 Author Share Posted January 4, 2005 There is easily an inch worth of threads GONE! I just borrowed an extensive TAP and DIE set from my buddy and will take a look at the damage this evening... I've got some stuff to do to the Vette to get it ready for the track event in February, so I'm going to redirect some of my time to it, since it is actually a working, running, driving car... Imagine that, a car that WORKS... Anyway, I'll get back to you guys and let you know what I end up with... Mike Quote Link to comment Share on other sites More sharing options...
Mikelly Posted January 4, 2005 Author Share Posted January 4, 2005 Well I'm Deaf... and Happy... I pulled the tap and die set Barry had loaned me out, and I ran the tap into the crank, cleaned out a TON of trach, and I found over an inch of good usable threads, So I'm gonna get a new Grade 8bolt and hone this balancer out a little, and then heat it up (AGAIN) and try it later this weekend... I'm deaf because I started the Vette with the new LGM headers, SLP Cats and rearward pipes installed... WOW... I really need the mufflers on now... Fortunately I ordered some new 02 sensors, and extended the wires to reach the harness from the new bungs and got ZERO codes and NO leaks... Musta done something right! Now I'm going to remove the whole rear suspension, trans and differential, install a new Torque tube aluminum replacement bushing (Factory was rubber) and fix a trans to diff leak I've had since day one... Then I'm done with this thing and it can go out to the exhaust shop to have the stainless 3 inch pipes bent to run back to my Bprla Stingers! Fun Fun FUn! Mike Quote Link to comment Share on other sites More sharing options...
Ferd/289 Posted January 5, 2005 Share Posted January 5, 2005 BillZ260, How do you remove a broken tap? Ferd Quote Link to comment Share on other sites More sharing options...
VRJoe Posted January 5, 2005 Share Posted January 5, 2005 You need a broken tap remover. It has four fingers that slide into the low points of the tap and allow you to turn the tap back out. I've been able to got some out with a good pair of needle nose pliers. Others I've had to drill out. You'll need carbide tipped drills to drill out a broken tap. If it's not in too far and you can get to the back side you can drive it out from the back with a drift pin, it screws up the threads you tapped, but it gets it out. Been there, done that. - Joe Quote Link to comment Share on other sites More sharing options...
datsunlover Posted January 5, 2005 Share Posted January 5, 2005 Just wanted to clarify something, there are NO "interference" fit threads. There ARE thread "FIT" classes, ie: Class 1-4, 1 being Loose, 2 Free, 3 Med, 4 Close but not tight. The class 4 thread movment between the nut and bolt feels almost like a wheel bearing. You can't really spin it, but it easily turns. Any threads that are difficult to tighten are either cheaply mass produced or the wrong size. True.. my bad.. I ment to say "almost like an interference fit" and 'feel' tight as you spin them on. Sorry for bad info there... And on the tap extractors.. I've never had one work very well. Ussualy just end up trashing it, or breaking it off; so now you have a tap AND pieces of extractor to drill out. I've used needle nose pliers quite a bit, or if there's enough sticking out, a good pair of vice grips works sometimes. Quote Link to comment Share on other sites More sharing options...
Jolane Posted January 5, 2005 Share Posted January 5, 2005 To remove a tap...if it is in aluminum, such as a head, you can burn the tap out with either a special machine that burns taps, or use chemicals to etch the tap away. You can also sometime beat the tap with a cold chisel and shatter it, and pull the pieces out carefully. I have also successfully used a die grinder and several grinding bits to wittle a tap out...none of these methods are fun though! Joshua Quote Link to comment Share on other sites More sharing options...
buZy Posted January 5, 2005 Share Posted January 5, 2005 Drill it out and go the next size thread up. I did it once on an old sbc pick-up truck. It worked geat and was easy to do. Quote Link to comment Share on other sites More sharing options...
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