Oil Drain Plug in the O2 hole?
 

My FlexFuel sensor already replaces the rear O2 Sensor from the stock Exhaust manifold. I'm installing headers now and don't really see the point in installing the O2 sensor back into the rear hole. (hehe) I found an oil drain plug that fits. Will that seal with a copper washer and take the heat ok long term?

It'll be just fine :)

Or you could put wide-band sensor in.

What would that do for me and where would I connect it? The second O2 connector has my FlexFuel sensor in it.

Wait, so the first sensor hole in the header has your primary O2 sensor in it, and the second hole has a flex fuel sensor in it? What other hole are you looking to plug?

No. The electrical plug for the secondary O2 sensor has the flex fuel kit plugged into it. They removed the now unused sensor from the header, and plugged the hole.

Right, the rear O2 sensor was still in the header, but disconnected. The Delicious Tuning FlexFuel thing was plugged into the electrical port where the O2 sensor would have been plugged in.

Doh! That makes sense now... :bonk:

As for the second hole, I would just plug it with the extra sensor OP has instead of taking the chance on something that probably fits and seals, but we aren't sure how it responds to exhaust levels of heat. But that's just me.

Some headers come with plugs installed in the holes and leave it up to the end user to figure out where you want the sensor, or if you want to run one at all. You can pick up plugs with copper washers on Amazon for about $6.

If anyone needs the info, this is the one I got - had to add a matching copper washer because this comes with a rubber one.

https://www.oreillyauto.com/detail/b...090167/4177507

I decided against leaving the existing O2 sensor in for a few reasons.
1. I didn't want a disconnected O2 sensor wire floating around inviting questions at inspection time or just looking messy.
2. I didn't want the sensor sitting there getting hot and possibly failing in case I ever decide to go back to stock. I screwed it back into the stock manifold for safe keeping.
3. I like things to be clean and smooth - extra sensors poking out could only make installation more difficult :)

To a wide-band gauge.

How long is the oil bolt?
Will it protrude into the exhaust path and slow your roll?

That's a good point, and I checked that. After screwing it all the way down, its almost flush with the inside of the tubing, which is ideal. The hole where you screw it in is raised a bit.

This isn't mine, but it looks just like mine - you can see the holes for the O2 sensors.
https://i.imgur.com/6d0W02K.jpg

I would move your primary down stream and plug the upstream hole.