wysubey Posted July 8, 2019 Share Posted July 8, 2019 Pulled the Y pipe out today because of exhaust leak that is noisy and smells in the cabin when not recirculating cabin air. 2 studs stayed in the engine block, not stripped. 1 stud came out with the nut, engine block threads OK, but 1 hole on the L side is stripped. Won't thread back in at all. What's my best option... 1. Drill and re-tap larger diameter? Seems to be plenty of material to support larger hole an re-cut threads. New Y-pipe and cat have large slots (15ish MM) Never done that before though, might be tricky to align drill bit and tap? 2. Helicoil? Never used these either. 3. There are 2 other holes with threads 90 degrees rotated from the original ones. Is there a way to get a 2nd flange around the pipe rotated 90 degrees to use these holes? They have threads same size as the original ones. 4. Other ideas? I want to keep it as OEM as possible. i already have the replacement Y pipe and cat so I don't want to change that. Link to comment Share on other sites More sharing options...
FerGloyale Posted July 8, 2019 Share Posted July 8, 2019 Tap to 7/16th and install a 7/16th stud. Or helicoil. More work, more expensive, but then you retain metric stud if that's REALLY important to you. For the $40 price difference, less work, and leaves more material for later and stronger (no helicoil) I use 7/16th stud. Link to comment Share on other sites More sharing options...
GeneralDisorder Posted July 8, 2019 Share Posted July 8, 2019 (edited) Heli-coil. We use https://www.threadtoolsupply.com/ Get some EJ exhaust manifold studs from Subaru. GD Edited July 8, 2019 by GeneralDisorder Link to comment Share on other sites More sharing options...
DaveT Posted July 8, 2019 Share Posted July 8, 2019 I have used helicoils on mine, with good results. Yes, make sure the drill and tap are perpendicular to the face. Link to comment Share on other sites More sharing options...
idosubaru Posted July 8, 2019 Share Posted July 8, 2019 Helicoil and 7/16 are both easy. Tap it and done. Link to comment Share on other sites More sharing options...
Mack Truck Posted July 8, 2019 Share Posted July 8, 2019 yes me too on mine. i got a helicoil and fixed it right up, btw i make teh mistake and paid a lot for matching metric threads and pitch. my friend had one that as metric but not the same pitch, and for one bolt on the car it would have beeen a huge savings to use his that he will never use after the one bolt he replaced. so look around for the right drill bit and helicoil set just match the stud with a correct nut and your good to go. Link to comment Share on other sites More sharing options...
moosens Posted July 8, 2019 Share Posted July 8, 2019 Timesert is another option if you’re going long term and expect to remove the y pipe again. Pricey , but excellent. Link to comment Share on other sites More sharing options...
wysubey Posted July 13, 2019 Author Share Posted July 13, 2019 I ended up drilling & tapping new 12mm threads. Worked a treat! It's so quiet now! Thanks for the input all. Link to comment Share on other sites More sharing options...
Steptoe Posted July 14, 2019 Share Posted July 14, 2019 M12 ? Did you need to increase hole size on flanges? Always good to quieten a burnt outflange gasket Link to comment Share on other sites More sharing options...
wysubey Posted July 15, 2019 Author Share Posted July 15, 2019 No, my replacement Cat/Y pipe from rockauto has large holes in the flanges. They're like 15mm. I went larger diameter on the coupling bolts to the muffler too. Link to comment Share on other sites More sharing options...
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