I just noticed today that I have a 1/4" hole in the top of my downpipe right under the flange. WTF is this for?? Does it serve a purpose or should I seal it up with something? (<< How do I do that without welding?)

I'll post a pic tomorrow when I get home from work.

 

is it threaded, its probably for an o2 sensor

 

No it's not threaded, it's actually about 2 inches above the O2 sensor bung. Like I said, it's small... maybe a bit smaller than a quarter inch.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 91dxcrx &raquo;</TD></TR><TR><TD CLASS="quote">is it threaded, its probably for an o2 sensor</TD></TR></TABLE>

More likely an EGT bung.

 

I think it's too small to be for an egt pickup... and it's not threaded, it's just a hole.

 

Autometer EGT probe. It's 1/4" and one of the methods to mounting them are via clamp. So no need for threads.

 

Maybe I should just buy an autometer EGT guage and probe to seal that hole! J/k, I don't have the cash right now... I think I'll just chop down a big self-tapping screw and put it in there. At least I know I have a place for an egt probe in the future