How to install oxygen sensor bungs.
 

I've been asked this question a hundred times. I finally got around to taking a few pics when welding in some bungs. I've done 10 of them in the last 5 days.
This is the way that I do them. I've found this to be the easiest, quickest and most effective way to weld them in. I'll post a brief description with each set of pics in the next few posts.

First, I drill a 3/4" hole through both pipes with a hole saw. We usually put them in the tailpipes or risers, but occasionally put them in headers as well. The following pics are from both CMI tailpipes and Gil risers.
After we drill the hole through both pipes, you are left with a small gap between the 2 pipes. This is the water passage where the water that cools the exhaust travels. This passage must be sealed off so that no water gets into the tailpipe or onto the O2 sensor. The other way to do it would be to weld the bung on both the inside and outside to seal it. The problem is that you really don't have access to weld the inside. In 99% of the cases, it just isn't possible. So, we go about it a little differently. Once the holes are drilled, you must assess the size of the gap between the pipes. They all vary from pipe to pipe and even in the same pipe, depending on where you drill. The gap never stays symmetrical throughout the entire pipe. If the gap is small enough to just weld up, then great. You can just close off the gap between the pipes. If it's more than about 1/16", I will close it up some before welding.
The way we close it up and by using the rounded end of a ball pein hammer. I set the hammer in the hole and hit it with another hammer. The rounded edges of it will roll the edges of the outer pipe in toward the inner pipe. Once the gap is small enough to weld shut, then weld it up.

In the above pics, the holes were drilled and the gap between the pipes was closed off some. In these pics, the gap was welded closed.

At this point, I will check to be sure that the water passage is completely sealed off by pressure testing it. I made a rig with a piece of rubber hose, a ball valve and an air hose fitting. I hook up my hose to a shop air line and clamp it to the water inlet nipple on the pipe. I then open the valve and start running air through the pipe. At the same time, I spray a mix of Dawn soap and water all over the welded area. If there are any leaks, it will bubble. Hopefully, there are no leaks. If there are, this is the time to fix them. You can easily to back in and touch up the welding to repair any spots. You could also run water through the pipe to check for leaks, but there is really no way to build any pressure, since the ends of the tailpipes and risers are open to let the water out. I find the air and Dawn soap work better.

Once I am 100% positive that the pipe is completely sealed, I can then weld the bung in place. This is the easy part. It just gets welded to the outer pipe, which is a breeze.

Finally, here are some shots of the bung being welded onto the outer pipe. I will tack it in a few places before welding it in completely. Without the tacks, it will want to move around a bit.

Now, by NO means, do I consider myself a welder. I've done a ton of MIG welding, but the TIG is still something that I haven't quite mastered yet. So, for all of you welders out there, don't criticize my welds to much. It's one of those things that requires a ton of practice. Fortunately, I got quite a bit of practice this week.

For the guys that can't weld or don't have a welder, you can drill your owns holes, close the gaps and send it to the nearest welding shop for completion. Any competent welder can knock it right out.

Here are a few shots of the bung being burned in place.

I hope that this helps some of you when trying to install bungs.
Eddie

Great "how to" thread, Eddie. I would love to put a set of bungs in my Lightning headers, but judging by the experiences of other here on OSO who have tried to add O2 sensors to Lightning headers, I am afraid that my sensors will end up getting wet. I wish someone could develop an O2 sensor that could withstand a little water on it.

You welds look pretty good to me! You should see the ones I try to do - looks like a big old caterpillar. :) Someone could just take a sanding roll and a polisher to those welds and get them looking just fine.

Nice looking welds! I am running O2 sensors in my lightnings with no issues. I just bought a new set with the bungs welded in by Lightning.

I haven't installed any bungs in Lightening headers, but I've talked to a buddy that has done a few. The biggest problem he had was dealing with the steel inner and SS outer pipes. It required a very specific filler rod from what I remember. I think they also offer a full SS header. That would be much easier to deal with.
I don't see any reason that you can't put a bung in a Lightening header and keep the sensor dry. If it is installed just at the beginning of the collector, there is no reason that it shouldn't work. If there is water getting there, it's also going in the engine.
Eddie

Exactly how I did mine following your instructions on another post. Worked great and the pics make it easier to understand. Not that it's that hard anyway...

Glad that I could help Apollard.
Eddie

Eddie you are correct, welding Stainless to Carbon requires a 309 filler rod. Then i use 316L on everything else. Looks good and the only thing i would do different is to purge the area between the pipes (the area you pressure test in) with Argon. You will need another flow meter and line to do this. Just lightly purge this area for a minute prior to welding to remove all the oxygen from that cavity. You may have to play with the Flow as too much will mess with ur arc.Tape off the opposite side that your argon is being feed from and place a small hole in the tape to let the argon flow through and out going by the welded area. When done ur weld on the inside will look like the outside weld with no SUGAR or porosity and be a much better weld. Leave the purge on while welding in the Bung too this helps that weld become a better weld too.