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GTO no more baaah!
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1,150 Posts
Discussion Starter #1
I'm on day 2 of my Magnaflow catback exhaust install. Day 1 ended abruptly when I could not get the stripped front o2 sensor back in the stock midpipe. I drove an hour or so to the closest place that had them (Paradise Chevrolet-Cadillac) and bought a new one. I figured since the old one was all stripped out, a new one should go right in. Wrong!
I am beginning to damage the threads on the new one trying to screw it in and decided I had better stop before I have to go spend more money on the stupid sensor.

If the threads on the midpipe are damaged, what can I do to fix besides buying a new midpipe ($$$$$) I'm trying to put the stock midpipe back in with cats because the catless mids stink and don't make significant power.

can this be helicoiled? OR do I even need to? What if I had a hardened bolt of the correct size (and what is that, if anyone knows) to recreate the threads that are damaged?
 

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Registered
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309 Posts
Take the mid with a fubared bung to a machine shop and have them run a tap down it. Be careful tightening the new one down as the threads may be shaky.
An exhaust shop could also cut the old bung out and weld in a new one, they're all the same size thread iirc.
 

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Black is Beautiful!
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282 Posts
You could find a tap the correct size and run it through the hole to clean up the threads. That should take care of it. You'll probably also want to clean up the threads on the O2 sensor before reinstalling it as well.
 

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DesertGTO
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138 Posts
If the majority of the thread is still there, you might be able to run a tap through it and straighten it. If the thread is completely stripped, like Jon01 says, have a new bung welded in.
 

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GTO no more baaah!
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1,150 Posts
Discussion Starter #5
I went ahead and dropped it off at a muffler shop. My install is now going to go to 4-5 days instead of 4-5 hours :(
I didn't feel like buying new tools today.
 

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"How big could it be?"
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480 Posts
Sorry to hear that. BTW, if this happens again, or to anyone else, go buy a spark plug thread chaser at the local parts store. Most of them have a 14mm and and 18mm end-the 18mm is the same as an O2 sensor.
 

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GTO no more baaah!
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1,150 Posts
Discussion Starter #9
I had JBA catless mids on there and I'm putting the cats back on because the smell and raspyness of the exhaust and -2MPG (YMMV) is not worth the 5RWHP. The sad part is, I'm already $$ enough into this to nearly match the quote Richard gave me to put the catback on, and my car is in the air with nothing from the headers back right now, LOL!

Despite the frustrations, I still enjoy getting in there and getting dirty and being "ONE" with my GTO and my wallet :D
 

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GTO went bye-bye
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1,455 Posts
ah, i see. FWIW, i went with JBA catted midpipes and the Magnaflow catback. tone is awesome and the voume isn't what i would describe as overly loud. don't know about the mileage. have my foot in it too much

Mike
 

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GTO no more baaah!
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1,150 Posts
Discussion Starter #11
Got all the pipes connected again but ran out of time so it's still in the air waiting for tightening and adjustment. I should be done tomorrow afternoon.
 

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Warranty Killer
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400 Posts
Sorry you are having problems! Mine literally took less than an hour, and went trouble free. In the end though, trust me it's worth it!

Gregg
 

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GTO no more baaah!
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1,150 Posts
Discussion Starter #13
Ya once I got the midpipes hooked up the rest went together in 10 minutes not including tightening/adjusting for clearance.
 

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not a pontiac its a HOLDEN !!
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8,787 Posts
o2 sensors are 18mm x 1.5 for reference

always put a little anti-sieze on the threads , but becarefull not to get any into the sensor itself
 
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