I am having a new engine for the 87 built and want to know if I should buy a new header.I have a pacesetter on it right now but it moved my o2 sensor from the manifold down to the midpipe by the cat.Now while I am cruising at a steady pace,the check engine light pops on and won't go off till I give it gas.It puffs out black smoke when I floor it but it still runs good.I looked inside the mid pipe and the o2 bung is so high above the pipe that you can't even see the sensor inside the pipe.Could this be the reason for the cel or would it be because I lengthened the wire for the sensor?I don't want to run rich with the new engine.

 

It could be either...
The repositioning of the sensor causing the lengthening of the wire may have reduced/increased it's resistance (it escapes me at the moment just which it would be... DUH!) if you went with the same gauge wire as it would be forced to carry the signal a greater distance in order to read it.

Repositioning the sensor away from the manifold, where there's a greater exhaust flow, should be o'kay as the flow does remain pretty constant.

By the same token, the sensor being placed so high into the bung and, basically, out of the exhaust flow that it reads may also be contributing to the faulty CEL signals.

I'd try grinding the bung down first to lower the sensor into the exhaust flow as the extended wire would probally be o'kay.

 

I just grabbed some wire that I had and lengthened it so that could have something to do with it.It definatley isn't in the exhaust flow.I may take the mid pipe off and take it to a shop and see if they can cut it off and weld it lower.

 

So change the wire out, solder the connection with your Coleman soldering pen and then put a connector on the joint that has heat resistant silicone squirted in either end, take the pipe to the shop and let them reseat the bung and you should be good to go.

p.s. And may the force be with you, young jedi.