Theoretically as the entire world would hate anyone who did this... Would anything be affected by welding a pipe in place of the cat? I've read concerns about an o2 sensor, but don't believe it's located there on my car? 91 formula 350 tpi

 

Ive done it with almost every vehicle ive ever owned. Some say it makes your car stink? No it does not. It does allow your engine to breathe. Im glad I don't live in some s#!Thole like California which requires them.

 

Nothing is going to break, you will smell it does not matter how good your tune is. Even modern cars will have an odor without cats.

 

TPI only has one oxygen sensor upstream of the cat.

My car doesn't have the cat and it is a 4.8. It smells a little of gas when it runs, not real bad though

 

you might be better off just gutting the webbing/material from inside the cat instead of taking the time/effort to cut out the cat and weld in a pipe. just hollow it out. therefore you don't have to cut anything. it involves dropping a portion of the exhaust and whatnot, but once the cat is hollow, it is essentially just a pipe

 

Oh no the California boogieman! out to get people that are ill-informed

High flow cats don't really impact the breathability of your sub 300hp SBC


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o2 sensor is before the cat. You might as well get the EGR tuned out and take off the smog pump and air tubes.

 

If you have no smog check issues where you live, yes, the cat can be replaced by a "test" pipe. But other than the additional cost of a replacement cat over the cost of said pipe, what do you expect to gain by removing it?

 

Wow , it must really suck to live in the smog rules laughingstock of the rest of the country while being into vintage cars .

I get it , being defensive of where you live in a territorial way is a natural reaction to living in such a place and hearing over & over how "commie" it is .

And before you go attacking me & my post , just know that I'm right there with ya , no I don't live in California but I know all too well about people throwing shade on where ya live ;

Consider yourself lucky that your not known by the rest of the country as a "Mashole ! Yes I proudly DO live in Massachusetts , whose slogan "Massachusetts the bay state" is commonly corrupted to "Taxachusetts the pay state" by a lot who don't live here .

I just smile , take a deep breath (on clean air days) and chalk it up to "coast envy"

 

Your car will run exactly the same. One of my cats developed a horrible rattle, as well as the car having a pretty significant power loss, and I will soon be cutting them out and putting in new pipe.

 

right under you in Connecticut orange bird, i believe we just took the spot as the most taxed state in the country. we had a horrible governor and then people voted in someone even worse than him just to keep the state blue.

 

Hi Tyler , Yep , I hear you and without getting too political things should always be "people before party" but sadly we know that's not how present day politics works . In fact , I believe it was no less than George Washington himself who was completely against the political party for just that reason , people will follow the party line even to the country's detriment .

Anyway , to try to remain somewhat within topic I'll say this ;

This is one of those "damned if you , damned if you don't" kinds of topics for me , because while one part of me says that yes of course you should be able to modify your car to your own liking (within road safe limits , of course) , the other part says why should anyone be allowed to do something that causes their car to foul the air worse than everyone else's (Cat equipped) cars do ? Like I said , I'm really undecided on this one , , but not wanting the guilt of mucking up everyone's air I do have functioning Cats on both of my cars

 

To be honest i just don't want to spend the $200 if it's not actually needed especially since emissions aren't an issue for me. Also, the car already smells like fumes from the old setup that's rusted to death which I'm replacing anyway.

 

none of my hollowed cat Thirdgens ever smelled...

If you sat behind the car the smell of the exhaust changes from a sweeter stock smell to “burnt popcorn”... it’s not more scent IMO, but it loses that stock GM exhaust smell... Not a huge deal... If your exhaust reeks of gas when you’re in the car, something else is wrong..

 

 

I'm not against emission controls on street-driven vehicles. What I AM against is the mandate that one must retain the old, outdated emission controls regardless of their inferiority. There shouldn't be visual inspections, only sniffer tests. Either your car runs clean or it doesn't. Modern cars have modern cats and don't have airpumps. You should be allowed to convert your old car to a more modern emission control system. That's my gripe...

 

Well said !

The bottom line , in my opinion also , is that in States that still do test antique cars for emissions , it should be that if you can make the car pass the sniffer with newer parts that should be enough to pass the inspection .

I Thank God every time I drive my car that it's a visual safety check only on anything pre OBD2 here in Mass.

 

You'll have 2 cats and 2 a.i.r. tubes to deal with if you do the test pipe.

 

My old 87 IROC without the smog and a hollowed cat would still pass emissions when they had that tailpipe probe... It would barely pass, but it would... So what was the purpose really? All it seemed to do was lower the performance...

There should definitely be different rules for cars that are clearly “not commuter cars”

Mass is pretty cool with the standards for classic cars.. my biggest gripe is that I can’t run 1988 mass plates because back then they didn’t have two plates... They are gently forcing people that still have plates from the 80s to turn them in... 60s and 50s cars get to run “year of manufacture” plates but the 80s cars will never be able to... its BS

 

I gutted my cat but left it in place. Can smell gas from behind the car but not while in it. One thing though..... it got a LOT louder, so much so that I'm now gonna replace the gutted cat with an "Cherry Bomb" style muffler.