I am having a friend weld some o2 bungs in for me this weekend.
I figured I would get the bungs at Autozone but looking at their prices they want $19 per bung and $12 per plug vs $7.42 for a combination from Amazon
(I will be getting 3 of each) http://www.amazon.com/Innovate-Motor...=pd_sbs_auto_1

Is there a certain type I need to get? Metal type? Size? Will these stainless ones work fine? I don't know anything about welding but I think I heard somewhere that it is hard to weld stainless???

I'm putting 1 in my cattman y-pipe for a wideband and 2 more in my factory exhaust behind the main cat (for extending secondary O2s)

 

I would definitely buy stainless bungs. mild steel + heat + water/brine = horrible oxidation on the threads. I think M18x1.25 is standard O2 sensor thread. Still you should use anti-sieze on the threads when you put in the O2 sensors. Your friend is going to TIG weld these, right?

 

I'm not sure he said it's a wire feed.

 

http://forums.maxima.org/all-motor/3...g-welding.html