So I've been sitting on this job for quite a while now. Finally have a break from school and am getting around to putting the new front pre-cat in. Got the old one out without too much trouble. Got the O2 sensor out of the old one. Started putting the new one in and I can't get it into place. I think I can get the bolts and nuts on the top part to attach to the exhaust manifold ok, the problem I am having is the bottom three bolts, the ones that attach to the OEM y-pipe. The OEM y-pipe appears to have some sort of internal metal bit that fits inside the pipe on both the y-pipe and the pre-cat, it is basically a pipe of smaller diameter to mate up both pieces. I can't get the new pre-cat to fit over that while still mating up to the bolts on the exhaust manifold.

Hopefully for those of you who have done this, you understand what I am talking about. If not I can post pictures later on.

 

Did you remove the old metal o-ring gasket when you took the old cat off? If not, my guess is that's what's sticking out of the OEM Y pipe.

 

Make sure you replace that Crush gasket

 

NJMax is this the gasket to which you are referring? It would make sense that it is supposed to come out, I just didn't want to go yanking on it when I wasn't sure.



MaxinO2 are you referring to the same gasket or to the other one (the one that goes on the exhaust manifold end?

I have this guy:


But on the new cat there is nowhere for it to go, the bolt holes all line up, but the design of the cat itself has nowhere this would go, not to mention the cat material is recessed further down into the thing so it wouldn't even line up to seal if it did have a place.

 

aftermarket cats use different gaskets. Thats not a problem, just make sure you have a gasket n there.

onto the y-pipe end, make sure you replace the crush gasket. Sometimes you have to grind the "step" in the y-pipe to make it fit the aftermarket cat. There is a reason why the aftermarket cats cost so much less than oem.

can you take a pic of the after market cat of the bottom part?

 

If the flange of the new front pre-cat is catching on the y-pipe then you need to install it differently, or as another person said grind down the flange. If you don't want to grind it down you can try installing with flange in first, then tilt up towards the bolts at the top. If that doesn't work you'll have to loosen or remove the y-pipe top bolts at the header which can be a pain in the butt.

 

The trouble is that you bought replacements lol.

 

New pics:

Bottom of cats, new one on left:


Top of cats, new one on right


Side by side, new one on top


And finally, the gasket, the new one did not come with any gasket, so this is how the old gasket fits into the new one:
OLD:


NEW:

 

So if I flip the thing upside down, I can't get that flange to fit inside the new cat all the way, so I think grinding it is the only thing that will work.

Let me just ask to make sure, that flange doesn't come out right?

This whole thing has turned into a debacle, I am now considering buying OEM, $700 because I don't even know for sure that even if I grind it that the thing will fit properly. Because of the way it catches on the y-pipe flange, and the slightly more bulbous nature of the new cat, I can't even tighten the top all the way to see if that lines up.

Of course as I am out of the return period on the new cat I have, I would be out the money on that, unless I can ebay it or something.