O2 sensor placement?

Is it better to weld the bungs right into the headers or will I get better readings putting them in my collector extensions? My extensions will be 3"X24" long for now.

Thanks!

Put it about 6" behind the end of the primaries
and make sure its pointed downward so it doesnt
hold any water(above 9 oclock- 3 oclock).. dont
get to close to the end of the collectors so it
doesnt see the fresh air

Thanks Mike.

Agree, mines 6-7" past the merge just after the flange in my side pipes........

I read something that wanted them at least 18" from the end of the extension.

Yes, from what I've read too close to the outlet will cause lean readings. I want to do the best I can to not send myself in wrong directions to start.

You said you would be adding collector extensions.. so
you will be fine with what I said

Would the optimum location be different for a full exhaust system, rather than open headers?

A very simple test to see if your particular combo is likely to pull "free air" back to the wideband, is to let it idle, and put a piece of paper at the exhaust exit.
Seems crazy, but it is not uncommon for the paper to be pulled back against the pipe between pulses. If it does that, you need to move the sensor as far away from the exit as possible, or ignore the readings at low engine speeds.
If it does do this, be sure to get a good seal at the header to extension connection.

An O2 manufacturer, cant remember which one, said rule of thumb is 36" from closest exhaust port.

And make sure you can get the damn thing screwed in after everything is installed.

FYI...It's of major important you don't have any exhaust leaks prior to the O2 sensor.

Looks like 6" back from the primaries puts them about 4" from the exit flange. I can point them straight out to the sides and be able to get them in and out.

Thanks everyone.