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| Broke the bolts on the choke housing https://slantsix.org/forum/viewtopic.php?t=42814 |
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| Author: | Josh P [ Wed Dec 08, 2010 1:07 pm ] |
| Post subject: | Broke the bolts on the choke housing |
So this morning while converting to a fancy new electronic choke I broke the bolts that hold the choke thermostat housing to the exhaust manifold... So tomorrow I will be drilling and retapping the holes. Anybody have the correct thread count and bolt size? Or should I tap it will something a bit smaller/larger? |
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| Author: | 4speed [ Wed Dec 08, 2010 2:53 pm ] |
| Post subject: | |
Try soaking the broken stud with thin penetrating oil (not WD40) over night and then use a left hand twist drill or a center drill (try MSC Catalog) to remove the stud. Some times as you drill and the stud gets hot it will un-screw its self, worth a try. About 50/50. Even if it does not work you will end up with the pilot hole in the center to drill out with. win-win. |
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| Author: | Doc [ Wed Dec 08, 2010 4:32 pm ] |
| Post subject: | |
Those are 1/4 - 20 unc threaded holes. DD |
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| Author: | Josh P [ Wed Dec 08, 2010 11:19 pm ] |
| Post subject: | |
Quote: Those are 1/4 - 20 unc threaded holes.
Thanks so much Doc. Am I right to retap them the same size and thread count? Or should I go slightly larger or smaller?DD I'm wondering if retapping with the same specs will damage the original thread and kill any attempt to create new threads? And if I should go bigger, what would be a good size? |
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| Author: | slantfin [ Thu Dec 09, 2010 5:30 am ] |
| Post subject: | |
Maybe you could use the correct heli-coil insert for a 1/4" bolt. Then you could use the same-sized fastener. |
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| Author: | Doc [ Thu Dec 09, 2010 8:43 am ] |
| Post subject: | |
Removing a broken bolt or stud is a pain but if approched right, you can restore the original thread. The "trick" is to carefully center-punch the broken "stub" and then use a smaller pilot drill to get a well centered hole started. Once you have a pilot hole, work with progressively larger drills, to open the new hole up to the minor thread diameter. At this point, you should start to see a "fingerprint" of the original thread showing, then you get a tap and use it to clean-out the remaining material stuck in the "V" of the threads. Many times, I get the "sleeve" of the old fastener to jam onto the tap, then it un-threads from the hole. If that process fails, install a thread repair insert. DD |
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| Author: | Josh P [ Thu Dec 09, 2010 2:17 pm ] |
| Post subject: | |
Thanks everybody, it all worked out and I was able to restore the original threads. I ended up center punching both bolts and using a smaller drill bit and another bit just smaller than the threads. Almost all the bolt came out, and I got the remaining bits out using a tap as Doc mentioned. I also got my electric choke in place and it works great, its been a good day. Now if only my magnecor wires would get here... |
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