Removing "cat" from older car?

I have a very low mileage '85 Caddy Seville. It is time for a new muffler and I am wondering about removing the catalytic converter. Will this make any difference? The car is severely underpowered and even 5 hp would be noticeable. Is there any other antique smog equipment I can remove? My state does not check cars this age. this is the 4.1, not the 8-6-4.

I'd say yes especially if it's original CAT because it may be clogged. You could hollow it out and put it back on. Take a steel rod like piece of rebar and hollow it out or a piece of replacement pipe and you'll get a bit better flow but probably only notice the sound difference and not the extra hp.

From what I know that's a fuel injected V8 and I'm sure it relies on an upstream O2 sensor and if it is in the cat on the upstream side you'll need to retain the O2 sensor for engine (fuel injection) management.

I know on the 80's Mopar there is only one O2 sensor pre-cat, my 88 CSX-T is cat-less and doesn't know the difference.

If the CAT looks like this then it would free up exhaust flow but how much power it would gain I am not sure.

This old style of CAT had ceramic balls in it coated with platinum/iridium. They choked the exhaust pretty bad.

Later styles up to today have a honeycomb matrix and flows much better and restrict flow very little, assuming it is not clogged or clogging.

As for the O2 Sensor and EFI. EFI systems require at least one O2 sensor before the cat. The cat cleans up the exhaust and the O2 sensor for the EFI needs to see how dirty or rich the exhaust is to adjust the air/fuel.

The O2 sensors after the cat (95 and newer) have nothing to do with the engine running. They are there to sniff the exhaust and see if the cat is working. If the reading before the cat and after the cat are the same the cat has failed.

If you want to delete the CAT and stay stealthy cut it open and weld a tube through the middle. I do it from the top and weld the top back on. If you don't put a tube inside the cat housing it will have a definite ping sound as the exhaust echos in the hollow cat.

If you remove or gut a cat on a 95 and later system with 2 or more O2 sensors put a spark plug non fouler adapter or O2 Spacer between the REAR O2 sensor(s) and the exhaust. It pulls the rear O2 sensors out of the exhaust flow and tricks the computer into thinking the cat is still there and ok.

Hope it helps.

I can only speak from experience- parents had an 85 coupe de ville with the 4.1. Its a massive turd. You could do a bunch of stuff to it, but naturally aspirated its a dump box, and are infamous for rear main leaks.

About the cats, I pulled a clogged cat off of my mothers Dodge minivan in early Nov, this year (she replaced it with a new one, her money). That OEM cat, at the junk yard, was worth $300, I suspect if I would have resisted a bit, I believe could have gotten more! Before you cut one up, might want to see what its worth scrap. Gene

The druggies are stealing them for the money.

Yes, I understand "factory" cats are worth a good piece of change. Aftermarket replacements, not so much. About the druggies someone else mentioned. Without a doubt. I live near a commuter rail station. Not safe to park a modern pick up there, they cut the cats off with a battery Sawzall.

Yeah, no power, I think 150hp. That is why I was looking for even 5hp. Car & engine only have 60K, so far, so good. I like it (I know it is love it, or hate it) and may swap the engine when I have more energy. It looks like this one, except later alloy wheels. I just stole the picture, no idea about the other cars.

We used to do this back in the day when cats got clogged up. They also used to sell "test tubes", pieces of pipe that bolted in to replace cats. Marketed as a diagnostic tool to run while you ordered a new cat. Guess how often the test tubes were removed...

Yeah, I remember those in the J.C. Whitney catalogs, remember those?

Sounds like time for an LS swap to me!

That is the favored swap for them at the moment, particularly LS4.

in my experience "unclogging" cats, most guys just do the "jam a pipe into them" pick out the big chunks, and call it done.
then said "jammers" complain afterward the car ran better, but it's now back to where it was, or worse.
the problem with doing this on the car [or off for that matter] is you get the big chunks, but not all of the material. what's left will eventually find it's way to the muffler, then clog it up, choking off the exhaust.
the only sure fire way was mentioned above. take the cat off, cut open the top, remove the material, then weld the top back on. that way, you can be sure all the material is gone.
or get a "test pipe" [made or bought] installed.
i have fixed too many "jammer" repairs over the years, and heard them cry about buying new mufflers.
anyone that talks about punching out cats these days, i just tell them to not come back complaining to me when the car starts to run worse than before.

When I read the title of this thread a totally different image went through my head. A long time ago my wife's brother asked thier dad if he could borrow his car to go on a date. Dad said you have a good car , take it. He said but my car stinks real bad I can't take it on a date. Dad says let's find out why it stinks. They opened the hood and there was a dead cat laying on the intake manifold. Dad tried to pull the cat out by the leg and the leg just pulled out like an overdone turkey drumstick.

When I was a kid, I found a cat trapped between my battery and the hood.

I had no choice but to remove the cat from the '88 Dodge Ram V6 I've been putting back together. Not only did the truck not come with a cat, an OE one is not available and aftermarket ones are pointless since the truck is over 25 years old and exempt!

Some vehicles, it's as easy as cutting them out, and welding in pipe. Some vehicles, like my Ram, had an air tube run from the air pump and not only pumped air into the manifolds, it pumped air into the cat as well. These are the ones you gotta watch out for because you don't want those air pipes turning into exhaust leaks. Since my air pump was also gone, I figured I'd delete the tubing and plug off the manifolds. Well, those plugs would've wound up being really odd sizes and drilling the holes bigger in my case, just wasn't an option. Not only that, a y-pipe for the V6 Ram is unobtainium. But I could find a y-pipe from a Dakota.... but that necessitated finding Dakota manifolds. THAT actually turned out to be a stroke of luck because '94-and-up manifolds no longer have the air injection ports.

But then, I needed a Dakota trans dipstick tube. because the one for the Ram manifolds ran right where the Dakota manifolds run. Ugh. What a debacle. Luckily it all worked out in the end.

Some people are lazy, you gotta jam that pipe through, then drop it a few times, then jam it again, don't stop until you can see clean metal around the edges lol. Or so I have heard.

I was unsuccessful at keeping Lucky (RIP) out of my Dart during construction, until I finally put the glass in

Did Chrysler ever tell their customers why so many of their factory catalytic converters broke up inside, rattled, then plugged?

Chrysler ended up putting 2 free replacement cats on my truck.

That had to cost at least $1000, maybe even +2000.

Multiply that by the number of vehicles they sold in those years.

Maybe the catalytic converter supplier had to pay all or part of that huge bill.

I remember my father's '77 Cordoba, which had a huge sign on the driver's sun visor "Do not Park on Grass"

Technically emissions equipment is federal and it's illegal to mess with. But my excuse to remove it would be it's bad and the part is no longer available,

Unless it's clogged it won't make much if any improvement removing it. The lack of performance is because of the 4.1. That's one of the reasons the earlier models of those Cadillacs are the ones people want even the ones with the 8-6-4.

I understand the problem. Long term solution is a swap to an LS4.

I usually put them in one of those cat caddies, and remove the feline from the car. Just drive the 64 Plymouth instead!

Did you ever get the cat out of the car,it's getting pretty cold out there these days! It was 14 degrees in Attleboro this morning!

What more can you ask for than some pussy and a tunnel ram dual quad intake manifold for a Hemi!

It's a 2x4 manifold... so, TWO pussies

Pretty soon you’re talking three-on-the-tree!

Jeez....Post an innocent cat picture and the Perv comments start flying...

I'm thinking the cat weighs more than a Hemi

Hey, I'm a blast at parties!