I'm placing my O2 bung in my collectors and I was wondering what size hole do I drill? Do I drill it big enough to where the O2 bung fits in the hole or just a hole that fits the O2 sensor, while the O2 bung sits on top of the collector? Thanks

 

You want it on top. That way you have more to weld to. Kind of depends on your welder though. You could do it the other way if you heli-arced it. I just put them on top of the hole and mig weld them since that's what I have.

 

alright and how far on the collectors did you put the bungs and it's not throwing any codes on ur car is it?

 

also someone told me to drill a 3/4 hole, is that what you did?