Drilling out narrow band O2 bung?
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Road Master
Joined: May 2005
Posts: 1,094
Likes: 414
From: Pennsylvania
Drilling out narrow band O2 bung?
I have a Cobra Speedster Slashdown exhaust with 12mm bungs for narrow band O2 sensors.
I'm getting target tune with wide band sensors, which require an M18 x 1.5mm bung.
Is there any reason why I cant just drill out that 12mm bung and tap it to the right thread?
I saw a photo of an exhaust with both types of bung, and while I'm perfectly capable of welding in the larger bungs,
I cant think of a good reason why I would need to use the 12mm for anything in the future, so why not just save some work
and just drill them out?
Am I tripping?
For all I know this may well be the common practice and I'm asking a dumb question, but my experience with exhaust systems is limited...
I'm getting target tune with wide band sensors, which require an M18 x 1.5mm bung.
Is there any reason why I cant just drill out that 12mm bung and tap it to the right thread?
I saw a photo of an exhaust with both types of bung, and while I'm perfectly capable of welding in the larger bungs,
I cant think of a good reason why I would need to use the 12mm for anything in the future, so why not just save some work
and just drill them out?
Am I tripping?
For all I know this may well be the common practice and I'm asking a dumb question, but my experience with exhaust systems is limited...
Stellar HDF Member
Joined: Jan 2017
Posts: 2,662
Likes: 2,065
From: Massachusetts
Traditionally, the wide bands should be closer to the exhaust ports than the narrow bands. Also , the wide bands are bigger in general, and depending on the current location, they may have interference issues.
Last edited by jake24lt; May 27, 2025 at 05:30 AM.
Stellar HDF Member
Joined: Jan 2017
Posts: 2,662
Likes: 2,065
From: Massachusetts
Thread Starter
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Road Master
Joined: May 2005
Posts: 1,094
Likes: 414
From: Pennsylvania
If you can believe it, that kit is over $400! A drill, tap and tap handle. 14900105
For an additional $377 I could have had the genuine Harley part. I'm sure I'll regret it for the rest of my life...
Stellar HDF Member
Joined: Feb 2006
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From: South Florida
At one time, didn't the V&H pipes come with a plug that the narrow bands screwed into, that you could simply unscrew in order to use wideband sensors? IDK if I am having a Mandela moment or if it was the way it was.
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Road Master
Joined: May 2005
Posts: 1,094
Likes: 414
From: Pennsylvania
This is why I was hoping to go the drill and tap method. At least can be reasonably assured the manufacturer gave some thought into interference when they designed the exhaust.
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Road Master
Joined: May 2005
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From: Pennsylvania
My understanding is that the pipes are extremely difficult to drill and tap. Something to do with the hardness of the metal. Curious to see how this goes.
At one time, didn't the V&H pipes come with a plug that the narrow bands screwed into, that you could simply unscrew in order to use wideband sensors? IDK if I am having a Mandela moment or if it was the way it was.
At one time, didn't the V&H pipes come with a plug that the narrow bands screwed into, that you could simply unscrew in order to use wideband sensors? IDK if I am having a Mandela moment or if it was the way it was.
This new set is a cobra exhaust, and it definitely doesnt have that option.
The Cobra pipes are 304 stainless which is definitely harder than carbon steel. I'm looking for some tips and tricks on line for drilling and tapping it cleanly.
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Stellar HDF Member
Joined: Jan 2017
Posts: 2,662
Likes: 2,065
From: Massachusetts
The last V&H exhaust I installed was 16 years ago, and I just traded that in on Saturday so now I cant check. My memory doesnt extend back 16 years for a detail like that
This new set is a cobra exhaust, and it definitely doesnt have that option.
The Cobra pipes are 304 stainless which is definitely harder than carbon steel. I'm looking for some tips and tricks on line for drilling and tapping it cleanly.
This new set is a cobra exhaust, and it definitely doesnt have that option.
The Cobra pipes are 304 stainless which is definitely harder than carbon steel. I'm looking for some tips and tricks on line for drilling and tapping it cleanly.
Thread Starter
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Road Master
Joined: May 2005
Posts: 1,094
Likes: 414
From: Pennsylvania
As I see it, aside from throwing all caution to the winds and trying it myself, I have 4 options
a. pay a professional to drill and tap the bung
b: pay a professional to weld in a proper bung
c: stick with the stock O2 sensors
d: pick a different exhaust system
Last edited by chunks; May 27, 2025 at 07:49 AM.