I bought a 1990 F250 with a 5.0 that I am getting back into shape. I have found out the previous owner changed out the exhaust from different headers all the way back to the mufflers. In doing so he got rid of the O2 sensor. The connector is zip tied to its harness.

I want to hook an O2 sensor back up and know I need to get a bung welded into the exhaust. The issue is that the location where all the header pipes come together (normal location for an O2 sensor I assume) is too far back from where the sensor connector is located. Would it be okay to put the sensor in one of the pipes or will I need to extend the harness somehow to put the sensor in the header collection area?

 

you can extend the wires on the HARNESS side if need be. you CAN weld a bung on one single exhaust runner, but you will get the best results if you have the bung after the collector. more accurate signal to report to the engine computer. i have extended both of my O2 sensor wire sets on my daily driver due to long tube header. as long as you extend the HARNESS side copper wires, and not the O2 sensor Aluminum wires, you will be fine. if you mess with the o2 wires the reading will be off and potentially cause AF ratio problems. hope this helps

 

places like summit also sell extension harnesses if you don't want to cut wires.

 

Weld a bung into the passenger side header collector, it won't make the engine run any better or worse than if it was further back where all the pipes collect.