MSefi.com read only forum (Jan.15,2018)

I have a 1981 turbo 301 pontiac firebird that is under conversion... the stock location for the O2 sensor was in the Uppipe pre-turbo. From what I'm seeing, you want the sensor to be post turbo? Are standard O2 sensors not as sensitive to the pressures pre-turbo, or did they just not know any better back then?

How much of a difference is it? I'm not looking forward to hacking the down pipe out so I can get the bung welded in. Right now none of the joints want to free up, so it may be angle grinder time. I'll do it if I have to, but if the up-pipe location will get the job done until this is tuned enough to get to an exhaust shop, that would be nice.

You'll want to move it to post-turbo; the sensor readings can be way off due to the excess heat and pressure. I suspect that Pontiac only used the O2 sensor for correction in a limited range at low flow rates that didn't build much heat or pressure in the exhaust.

Thanks for the info... I guess I just needed someone to force me to do it .

The only good spot I have to place it now is about 40-50" downstream. I've seen evidence in posts that this is doable, although perhaps not ideal this far away.

My down pipe is a bit mangled, and will ultimately get replaced. For now I'm using a band clamp O2 sensor adapter to put the fitting on the pipe, and the best spot as after the downpipe ends. I just want to get this up and running. When I can get this to the welding shop and have a new down pipe built I'll probably have a bung welded in about 20-24" from the turbo and then retune.