ChrisC Posted January 18, 2015 Share Posted January 18, 2015 Hi All I am posting this, because I am not sure I know how to fix the problem that I experienced today. I was in the process of attaching my gearbox back to my sigma engine, following the build manuals torque setting 47Nm (bell housing to engine) and 20Nm (bell hosing to sump) with new bolts and a new digital torque wrench. As I came to torque up the last bolt I heard a sound I haven’t heard for a very long time: the ping of a thread going in the block! The strange thing was, that I was nowhere near the torque setting (according to the wrench) yet.Ok, so ordinarily it’s a pain, but a helicoil kit and a bit of work will sort the problem, but not this time. The thread that has gone in the block is one of the two that are inside / combined with the locating pin for the bell housing. So, this means I can’t just drill it out and tap it again for the helicoil, because this would destroy the locating pin. There is also not enough room to fit a nut and a longer bolt, because of the shape of the casting of the block.I feel gutted, I don’t know what I have done wrong, it’s not like I don’t know how to use a torque wrench; I have been kicking myself all afternoon.I am hoping someone can come up with a smart solution to my problem. Or have I got to find another block? Link to comment Share on other sites More sharing options...
7 wonders of the world Posted January 18, 2015 Share Posted January 18, 2015 As the saying goes sh1t happens, but its recoverable,As the dowel is there to locate the engine to box you ideally need to offer another to replace this once after you tug it out to helicoil as you say above,put the engine and box together on the curent dowels and look for another suitable location in the similar area to dill a 6-8mm hole thro the bellhousing and into the block into which a roll pin can be inserted to act as a location dowel.Thats the locaton srted now just set to with the helicoil,We used to regularly drill out OE alloy threads and helicoil to give a stronger thread to prevent the threads pulling. Link to comment Share on other sites More sharing options...
Member Jonathan Kay Posted January 18, 2015 Member Share Posted January 18, 2015 Private Mail sentJonathan Link to comment Share on other sites More sharing options...
ChrisC Posted January 18, 2015 Author Share Posted January 18, 2015 Hi 7 WoundersRemoving the current dowel may be within my technical limits, adding a new dowel is a bit beyound my facilities. :-(Jonathan, PM sentChris. Link to comment Share on other sites More sharing options...
DJ. Posted January 18, 2015 Share Posted January 18, 2015 Sorry to hear that Of course it may not be you who broke the thread, it may have been over tightened the last time it was put together.Two possibilties I thought of:1. After the helicoil, you could fit a very thin steel collar around the bolt. You could cut the end off a similar bolt, cut a slot in the end and slide the collar over it. The bolt and collar would then locate the bell housing while you tighten the other bolts. Then you could unscrew that bolt with a screw driver and replace it with a proper bolt.2. Another way around it would be to open out the hole and re-tap the thread to suit a larger bolt, and drill a larger hole in the bell housing to suit. As long as the new bolt had an unthreaded section that was a precise fit in the bell housing hole, it would locate as well as a dowel.I think I would probably try option one. I hope this is of interest, but do act with caution as I do have quite a few years of mucking around with cars and other engineering hobbies, but I'm not a professional.Duncan Link to comment Share on other sites More sharing options...
ChrisC Posted January 18, 2015 Author Share Posted January 18, 2015 Hi Duncan I am like that, its sounds possible. I would have to remove the locating pin, helicoil the thread, and get a colar made to replace the existing pin, get a long bolt (cutting the head off so I am left with a stud). Put the stud in the helicoiled thread put the colar on the stud, the fit the bell housing. Once all the other bolts are fitted, remove the stud a and fit the bolt as normal (fingers crossed) That sounds like a plan, the best I have at the moment. Chris. Link to comment Share on other sites More sharing options...
ChrisC Posted January 18, 2015 Author Share Posted January 18, 2015 Any advice on removing the locating pin? Link to comment Share on other sites More sharing options...
ChrisC Posted January 19, 2015 Author Share Posted January 19, 2015 Can I fit a Helicoil from behind?? I have only every fitted a handful to Mini thermostat housings, where rust had eat the thread, but can they be fitted in reverse? i.e so the end the bolt goes in, goes into the repaired thread first and the bolt come in the from the opposite end from the repair? Link to comment Share on other sites More sharing options...
ECR Posted January 19, 2015 Share Posted January 19, 2015 If it's anything like the locations on my VX, it's just a thin tubular item and I was able to twist and rock/work it out with mole grips.Good luck ! Link to comment Share on other sites More sharing options...
DJ. Posted January 19, 2015 Share Posted January 19, 2015 That's a good question about a helicoil from the other end, sorry I don't know the answer. Link to comment Share on other sites More sharing options...
John Vine Posted January 19, 2015 Share Posted January 19, 2015 Can I fit a Helicoil from behind??Interesting idea. If you mean can you fit the helicoil so that the bolt is inserted from the opposite direction (into the base of the coil, as it were), it might be possible (but I've never tried it). I think it will depend on exactly how much of the tang remains when you come to break it off. If it's a clean break without anything protruding, you may be OK. It might be an idea to try it out on a spare coil before you proceed. Clamp the coil in a vice, snap off the tang and see whether you can insert the bolt. JV Link to comment Share on other sites More sharing options...
ChrisC Posted January 19, 2015 Author Share Posted January 19, 2015 I could run the bolt intital in the direction the coil was installed that should clean any bur left after the tang (didn't know what it was called earlier) is removed, fingers crossed. If that works I should be able to just do a simple helicoil repair, and not event remove the locating pin. I hope this works Chris. Link to comment Share on other sites More sharing options...
ChrisC Posted January 19, 2015 Author Share Posted January 19, 2015 Anyway helicoil kit ordered watch this space Thanks guys Link to comment Share on other sites More sharing options...
DJ. Posted January 19, 2015 Share Posted January 19, 2015 Good luck Link to comment Share on other sites More sharing options...
Martin J Posted January 20, 2015 Share Posted January 20, 2015 Sorry to hear of your bad luck Chris.It occured to me that if you were not really confident in recovering the sittuation why not (providing you can get it all in the back of car) deliver it to a good engineer with the necessary skills & equipment. This will hopefully save the block for you. Not that I'm saying your not capable but it can be a bit nerve wracking. I don't know, Mick Attree might be able to help?My late Dad was such a clever engineer with a really good little machine shop at home & often busted bits of engine would be brought to him & he had the skills to recover the sittuation.If you effect a repair yourself you will of course have immense self satisfaction. Link to comment Share on other sites More sharing options...
ChrisC Posted January 20, 2015 Author Share Posted January 20, 2015 Trust me if I am stuck it will be going to a decent engine builder, but I have helicoiled a head and block before (just not ally).We will see what happens at the weekend. Link to comment Share on other sites More sharing options...
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