This may sound stupid but how do you hollow out the cat on our cars?? I have heard all you have to do is "knock out" the material on the inside?? Is this easy to do and what else is involved? The reason for me wanting to do this is my car is a 95 and has the original cat on it and if its not doing me anygood anyways then why have it restricting my exhaust flow right?? I am sorry this sounds like such a newbie question but it is something that i want to do..........thanks in advance.


Chris

 

A screwdriver and a BFH. It's going to sound different, louder and raspy, you've been warned.

 

I've heard of taking a pipe and cramming it in there, push down on the cat with a pipe in the bottom opening and slam it against a sidewalk to break up all the catalyst and knock it all outta there. Just what I've heard.

 

Sorry for another stupid question but what is a BFH?? And i like it loud, my cutout is open 24/7 and even with that combined with the AS&M headers it is not loud enough for me!! So i am guessing its pretty simple. Like a 15 or 20 minute thing??



Chris

 

I've never heard the term before but I'm assuming it stands for Big F---ing Hammer.

 

LOL.........nice. SO basically you just get all of the material out. If so then i guess its pretty self explanitory?? Do i need to replace the gaskets or anything?? And it just unbolts and then bolts back on right??

 

Yep.. just get the insides out and bolt it back up.

As mentioned before though, it's going to change the sound of your exhaust. And they don't just mean making it louder. I've heard of a lot of people not being happy with the sound a hollowed cat makes. It supposedly makes a very hollow, tinney sound, which is why some people just remove the cat altogether, or they gut the cat and then run a straight pipe through it so that it's actually just a straight pipe, but looks like it has a cat.

 

Yup, Big bleepin Hammer.

The tinny hollow sound is what i was warning about. It will also almost bark or shreik in the mid rpms. Hard to describe, but there is a good chance you won't like it, it's not a good loud.

 

I use the handle from a small jack to break it up.
You just need some type of pipe adleast 15 inches long and a hammer. Beat the pipe into the ceramic honeycomb stuff and keep turning it over to dump it out. It makes a mess so use a big garbage can to dump it in.

 

My friend used a hockey stick and just rammed it in there to break up the stuff and then dumped it in the trash. I got a y-pipe from a guy on this board who welded in a straight pipe in place of the cat. My car sounds a lot better than Scott's car, who just hollowed out the cat. If you know someone who can weld, I'd highly advise you to use a straight pipe instead of simply hollowing out the cat. Or, you can hollow the cat, weld in the pipe, and then wrap the cat around the pipe and tack it in place so it looks like its there (what FyreLance said). Oh yeah, and to answer your question about gaskets, there are none, unless you take off the manifolds. The y-pipe doesn't use gaskets, just flanges. Soak the bolts in some PB blaster the day before.

 

what are the performance gains?

 

get a Off road pipe in there instead of hollowing it.

 

I agree, save your cat because there is a good chance you wont like the sound of the car without it. I just removed my single cat that I have had on since I installed single cat SLP's. I had an ORP/cutout put in it's place and made it so I can swap the cat back in if I didn't like it. I ran it for two weeks with the ORP and just yesterday put the cat back in. With the headers/ORP it made the Borla catback sound like crap I thought. It sounded great at idle and WOT but I didn't really like anything in between. The exhaust note sounded really ghetto to me, too much of a "thumpedy -thumping" noise when accelrating in the midrange, sounded like I had a 55 gall drum in the back. Maybe it would sound ok with a stock exhaust (which I assume you have) but I hated it with the Borla. For now I think I'll just use it when I go to the track.