Stainless Welding

[sjaroslo]

I have a set of Stainless Works headers that have the existing O2 bung pointing out-right at the side of my subframe; there's no way there's enough room to get an O2 sensor in there. On the other hand, there are gobs of room off of the collectors towards the inside of the header. So, I've purchased additional SS weld bungs from Stainless Works (as well as SS plugs for the existing ones), and I'm wondering, who should I be approaching about cutting in a hole and welding in the bungs? Is this something that any competent Exhaust shop in the area should be able to accomplish for me or should I be looking at Welding and fabrication specialists who work in stainless steel? I live in the Silicon Valley area of California (San Jose/Santa Clara) so if anyone has any specific suggestions for an appropriate vendor, I would be grateful to hear it. Thanks.

[gak68]

I would drill a pilot hole then use a step bit to get up to the desired size. I would find a exhaust or welding shop that can tig weld it on for you and fill the other hole.

[parsonsj]

If you have the header TIG-welded, ask the welder if he back-purges. If he says "no", or it's not necessary, find someone else.

If the welder MIG-welds the boss, ask them to use ss wire. If they use ordinary steel wire and 75/25 mix, your header will rust.

jp

[sjaroslo]

Thanks much for the feedback.

[80proZ]

Why would purge welding it be necessary? Do you realize how few people know how to purge weld properly. A hole saw( Lennox brand) would be fine!

[parsonsj]

Why would purge welding it be necessary?

I've not heard it called purge welding -- not sure if that's the same thing as back-purging. If it is the same, if you weld the bung into the collector without back-purging, the weld will "sugar" on the inside, restricting airflow (slightly), and eventually rusting.

Do you realize how few people know how to purge weld properly?

No. Do you? Why does the number matter?

[80proZ]

It is the same. You could weld it without the purge and not sugar it. I do sanitary welding for a living and know plenty of people who can TIG but can't purge weld. If you can't purge weld it properly, you're just wasting gas and time!

[parsonsj]

Back-purging is just equipment and setup, and takes little skill. The physical act of TIG-welding (torch and filler rod) is the same whether the weld is back-purged or not.

I guess I'm quibbling with your verb ("can't"): I would agree with "don't" or "won't", but not "can't".

[dontlifttoshift]

I don't back purge our exhaust if it is not getting polished, it's not worth the time. Fit up is key, perfect fit with no gap allows you to fusion weld all the seams with no sugaring.....it just doesn't get that hot on the backside. I haven't had a failure and have been doing it this way for 10 years.

There is a large shop by us and all they do is sanitary stainless, they weld and polish all of our headers and all of our polished exhaust systems. They are well equipped to do it and they machine weld most of it. The backside of the welds are better looking than the front side when done this way. Parts that will see a real heat, like a header tube will require full penetration welds.

As far as the O2 bungs, anyone that can weld stainless together competently should be able to handle that for you. It will be a better job if backpurged, but I don't feel it is a requirement.

[80proZ]

Purge welding has very little to do with equipment and setup. A proper purge weld has to do with proper heat, travel speed, and a purge gas pressure. If all you're trying to accomplish is no sugar on the back of the weld that can be a done with lower heat and the addition of filler!

[parsonsj]

We've hijacked the thread, I'm afraid, but this is how I back-purge:



Are we talking about the same thing?

[80proZ]

Sorry. Didn't mean to hijack the thread.
I've read your article. It's a pretty good one and enjoyed it. I only had one complaint. The weld color of a purged weld would be darker because more heat is required to properly breakdown the weld seam. If you're purge(back purging) welding, the idea is to breakdown the seam so that it appears that it's been welded on both sides. Not just to keep it from sugaring. I can weld SS tube and achieve no sugaring without the need for purging. Our goals of purge welding are different. Your doing it for no sugaring, I need my weld seam to breakdown in order to achieve a sanitary weld.
I can't post pictures here from my phone but I could start a thread if your interested? I'm currently doing a sanitary job with 3" .065 SS.
sjaroslo good luck with your project.

[parsonsj]

I could start a thread if your interested? I'm currently doing a sanitary job with 3" .065 SS.

Hell yeah!

I'm always interested in learning more, and I'm sure I'm not the only one. I understand what you're saying about a sanitary weld -- any nooks or crannies becomes a hot spot to collect bacteria; which doesn't really matter for exhaust tubing.

[sjaroslo]

Personally, I think that this is great, don't mind the hijack at all. It IS over my head, and honestly I'm probably taking away from it the things that I want to hear:

"As far as the O2 bungs, anyone that can weld stainless together competently should be able to handle that for you."

But another good point I think is:

"If the welder MIG-welds the boss, ask them to use ss wire" That seems like a question I could ask that will help me to determine if the folks I'm talking to are competent to do the job AND it alerts me to something that I hadn't thought about, using non-stainless steel wire and the ill effects (rust) it could have down the road.

It is actually sounding to me like I might be better off looking for Welders in my area rather than Exhaust vendors--I think that 80ProZ's knowledge of the mechanics of the process is probably going to far exceed an exhaust shop monkey's level of interest/engagement, for example (no disrespect to any exhaust shop monkeys out there!).

I talked to Frank @ Prodigy and alerted him that having Stainless Works put the bung on the outside of the collector is a bad idea, at least for a Morrison clip in a Camaro. Plenty of room facing inward (if I can figure a way to run the wiring without burning it), but on the outside--not so much.

[80proZ]

If anyone is interested, I have a thread in the fabrication forum.