This is probably a stupid question, but I'd rather know for sure before hand.
My carb'd 85 had headers, true duals and stacks, worked awesome!
Then the motor blew. Picked up a tpi 87, and want my stacks and headers back.
I know I need 02's if I want to get better than 5 mpg,
Does it matter where I put the sensors?
They're shorty headers, better to put em on the header or after it? Or does it matter..? Thanks

 

Put them at the end of the header or at the start of the Y pipe

 

No Y pipe, I'm running true duals. Does that make a difference?

 

It really doesn't matter. Just put the o2 sensor at the end of one of the headers or in a spot that wont interfere with the engine or floor. Factory setups have the o2 sensor in the driver side manifold, so, the ecm is only reading one bank of the engine. It would be the same thing with your true dual setup. You would think that GM would of put the sensor at the end of the y-pipe so the ecm reads both banks. Might not make much difference but would be better than reading one bank for calculations.