This is a general question. I have a 1989 GXL that had a cat fail this spring, i bought I new cat and have it ready for emissions - but I liked the hp gain from the not substrate thing going on so I'm working on redesigning part of my exhaust.

@ Meineke the guy said he could not cut the weld at the flange where the old cat was welded on.

I was thinking it should be possible to sawzaw @ the flange and grind out any roughness from the weld.

What do you think?

Basically I'm trying to make my exhuast switchable from a cat for streets, straight pipe for autocrosses, and a ground pipe for loud noises and ear trouble (track).

(PS. Maybe at this stage it means I should just get a track car)

 

let me see if Im following you on this...
you want to make an exhaust system with flanges where the cat bolts on...so it can be bolted/unbolted and have a piece of straight pipe that can be put in place of the cat when you feel like it...

yeah you can do this - you'll just have to do some fab work, weld on some flanges and build the striaght pipe with flanges

 

question is more can I break down all welding material on the flanges that are already there?