This is probably a stupid question but do the o2 sensors go before or after the cats. Im doing longubes soon but i thought that on a stock car the o2 sensors are after the cats. I am going to be running cats btw.

 

The O2 sensors on an OBD-I system (93-95) belong in front of the cats. They need to read the exhaust to measure A/F ratio, before the cats alter the chemical composition. The sensors need to be in the collectors, close to the point where the primaries merge.

You might also want to consider converting to "heated" sensors for your 93, since that is the only year that did not come from the factory with heated O2 sensors.

 

Your O2 sensors are before.

 

ok thanx for the quick replies and thats exactly what i wanted to hear

 

I would think they go before the cats...atleast that's where mine are. I got the shop to make some hole in the header collectors to have them mounted. I'm not sure on the 93, but that is how it is in the 97. I am pretty sure they go before the cats.
JOHN