i have a 1991 f150 with 302 iv put headers on i put on hooker long tubes and there was a bung in the last cylinder pipe so i put the o2 sensor in that instead of making one for the collector...iv been reading that you should put it in the collector? is mine ok in the header?

 

Its better to be in the collector so that you get readings from more then that one cylinder. I guess its ok so long as that one cylinder is working at 110%.

 

Put it in the collector.

 

I still don't see how the O2 sensor can get an accurate reading at all from only one bank.

 

It wont be completely accurate, but its better then just the one cylinder.

 

All cylinders get the same fueling(there's only one fuel map for all of them) and because of that it technically doesn't matter how many cylinders are "sampled" by the O2 sensor because it's just looking at the ratio fuel vs air.. not the volume. That said... injectors get dirty and wear over time and each one won't accumulate the same amount of dirt or wear, so it's better that the sensor see as many cylinders as possible so that the overall fuel tables can be adjusted to compensate. Bottom line is.. putting the sensor on 1 cylinder is cutting it thin but if it sees a whole bank that is sufficient.