O2 ?
 

my O2 sensor is 8 1/2 inches from the end of the collector. Is that too close? I can make a collector extension [might help low end, so that would be a +]-if so, how much longer? or will it be OK as is?
this is the only place it can be, so I can't move it to a more favorable position
thanks
Rod in AZ

Re: O2 ?
 

Rod your O2 needs back pressure to work. I don't believe in using an O2 gauge to dial your car but it can save your engine if your going lean at high rpm. Do your testing with a long extension or a muffler and get your reading. Then run your extensions with a paint stripe and cut at the end of the paint burn. 'OLD SCHOOL'

Re: O2 ?
 

They do not need back pressure. That is, however, closer to the end than I would run it. I put mine right at the end of the transition. That is only good for WOT. To use the O2 for part throttle (I.E. return road) you need an extension. A muffler works well, or a 24" extention. I have a 24' with a 45 deg bend about half way. Reversion during the overlap cycle will pull clean air back in at low RPM & loads. Looks very lean on the O2. Works OK @ WOT.

Re: O2 ?
 

Does NOT work. Never did. You can cut your way all of the way to the cylinder head. Air changes. Not a reliable test. Leave it where it's at. You're making your own relationship to any changes anyway.