Well first off Im new to this forum and i just got a little carried away and read the first 50 pages for the 1st gens.

Im looking to replace my stock cat with a new one which is only a piece of staright pipe with a converter shell welded around it. Would I be able to just move the o2 sensor to the pipe in front of that since I dont have one after my cat now?

Also my truck is a 1989 w-150 318 tbi 3 speed auto.

 

i don't see why you couldn't.

 

There never was an O2 sensor after the cat in our trucks. Why do you not want to use the O2 sensor position in the manifold? Why would you want to put a cat on it unless you have to for inspection?

 

I think from reading some more of the pages on here last night I was mistaken, I think what i thought was a o2 sensor in the cat is the egr? So that takes care of the o2 sensor problem but as far as putting on a new one, I dont need it in the county I live in but in surrounding counties they need them for inspection so thats why I want to go with the straight pipe look alike. So if I did that what would my options be for the egr valve? Thanks, Josh.

 

The EGR valve is up on the intake manifold. Are you talking about the air injection tube?

 

Alright, I just got in from checking it out, theres a piece of maybe half inch steel tubing coming out of the top of the cat and it runs forward and turns into 3/4" rubber hose and I followed that and it runs up and behind the pass. side exhaust manifold and up and across to this thing that im not sure of but its directly to the right of the upper radiator hose and its bolted to the alternator and has another hose coming from it that I couldnt follow but it went back along the driver side valve cover. So now im a bit lost.

 

the line from the cat goes to the air pump i think.

 

The air pump provides extra air thru the injection tube to the cat so that the cat can burn off the pollutants. My alternator is on the passengers side. The air pump is on the drivers side.

 

OK, so what can I do to bypass this to replace the cat? Can it just be rewelded back to whatever I replace it with ( highflow, straightpipe, etc)?

 

You can weld it back in if you want it to be strictly cosmetic to fool an inspector or you can just eliminate it and the air pump will just pump to the atmosphere.