when I was repairing the oil line on my corvette i removed the catalytic converter to get access to the oil adapter fittings. Upon reinstall the screw in stud the threads were all screwed up. I attempted to drill it out and install a thread repair but the kit I purchased got dull, it did remove the bad threads leaving 2.5 full threads intact. To repair it I just grabbed a bolt and nut that was the same thread size as the original stud screwed it through the piece, threw a bolt on the back end and it worked until it didn't. During my last track day after the first session the exhaust came loose. None of the hardware came off but out of fear that I would end up losing the exhaust, I parked it for the night. I purchased a M10x1.5 exhaust spring kit this week and attempted to install that but the spring is too long. So here is what I did. I took a long m10x1.5 and cut the head off of it effectively turning it into grade 8 all thread, I cleaned up the threads and threaded it through the 2 remaining threads on the pipe, I then put a bolt on either side of the original threaded collar effectively creating a new stud, I tightened those bolts as hard as I could with an open ended wrench. I then reinstalled sliding bracket and using my new "stud" and the original stud tightened m10x1.5 bolts onto each stud applying equal pressure to ensure that the two plates were parallel to each other. Will this hold?
Since I did this, put the car away and then thought about asking the experts I didn't think to take any pictures, but I found a few pictures on the internet and drew a diagram to explain it all. so without further ado, here is 3rd grade math to go with 1st grade mechanical skill.
monday bump for those that don't spend sunday evenings on the internet (like me :) )
Looks like it should hold up fine as long as none of the threads work themselves loose (which could happen more easily with your rigged-up fix), so you may want to add some high-temp threadlocker just to be sure.
GameboyRMH said:
Looks like it should hold up fine as long as none of the threads work themselves loose (which could happen more easily with your rigged-up fix), so you may want to add some high-temp threadlocker just to be sure.
i had read online that threadlocker doesn't work on exhaust pipes because the temp can easily exceed 400 degrees. is that not the case?
also when you say threads work themselves loose are you saying that one of the bolts that secures the threaded rod to the right side could get stripped or that they would vibrate loose? The first time I repaired this I used a bolt that went left to right on the diagram /w a nut on the end and on track the bolt/nut combo worked itself loose. I don't really want to waste another precious track day with a solution that isn't optimal given the situation. I had thought about threading the bolt the other way but the bend of the pipe doesn't allow you to get a long enough bolt in.
In reply to ClearWaterMS :
Most threadlockers won't work at high temps but there are a few high-temp threadlocker compounds available. I'm thinking the threads could work loose due to vibration, and now with two nuts on a threaded rod doing the work of a bolt there are more places it could happen.
Either way you have bolts in a high temp environment holding something together. Now you just have twice as many. One of those bolts isn't really doing anything (the one in the middle), the other is simply replacing the threads, so you are kind of right back to were you started (4 sets of threads holding it together, though one might be a bit shorter than the original stud threads).
I would say, it has the same chance of coming apart as the original setup.
aircooled said:
Either way you have bolts in a high temp environment holding something together. Now you just have twice as many. One of those bolts isn't really doing anything (the one in the middle), the other is simply replacing the threads, so you are kind of right back to were you started (4 sets of threads holding it together, though one might be a bit shorter than the original stud threads).
I would say, it has the same chance of coming apart as the original setup.
i think the one I'm most worried about coming lose is the one on the right side of the diagram. Vibration and expansion as a result of heat is what i'm worried about. The factory setup has never had a problem.
GameboyRMH said:
In reply to ClearWaterMS :
Most threadlockers won't work at high temps but there are a few high-temp threadlocker compounds available. I'm thinking the threads could work loose due to vibration, and now with two nuts on a threaded rod doing the work of a bolt there are more places it could happen.
can you recommend a specific product?
Just run bolts all the way through and use Nord-Locks. They're the best solution for high-vibration/stress environments IMO.
tahnks for the tip, I bought both the washers and the locktite, because if one is good, both can't be worse and missing a track day is way more expensive than an hour of work and $25 worth of stuff.
Why don't you just run a long bolt through the backside of the flange the stud threads into? Just snug it up and you're set - put the nuts on the two studs (one stud and one bolt) and you're done? Use mechanically locking nuts if you'd like.
I mean, my e36 uses long bolts and nuts and the bolts just slide through large holes in the flanges on either side of the joint.
Nordlocks suck at exhaust work. They work for vibration. They do not work so well for thermal expansion. At least that has been my experience multiple times.
Long bolts with spacers help keep the clamping loads with some expansion.
jfryjfry said:
Why don't you just run a long bolt through the backside of the flange the stud threads into? Just snug it up and you're set - put the nuts on the two studs (one stud and one bolt) and you're done? Use mechanically locking nuts if you'd like.
I mean, my e36 uses long bolts and nuts and the bolts just slide through large holes in the flanges on either side of the joint.
i tried that originally but the shape of the pipe and you can't line up the bolt such that you can screw it in. This is why I did what I did which was to thread a bolt in, tighten it on both sides of the flange which in theory by getting it good and tight means that I stretched the bolt just a bit and made a stud then screwed on the coller with bolts on both sides... I'll throw some of the 400 degree lock tite on it, I have driven the car around 200 miles already and haven't heard any exhaust leak so far.
