How much power gain do you get with a 2.5in staright pipe were the cat is supposed to be? With stock exhuast everywhere else. Its on an LG4.

 

you will maby gain 5hp if it doesnt screw up the computer..

You can still turn with a 500hp car its just the rear end slides around like its on ice

 

Not enough for the hassle of doing it at all. I'd keep it on.

 

It won't "screw up" the computer. The LG4 computer doesn't think that hard. Mine hasn't been touched.

On the other hand, like IROCThe5.7L said, it won't make a difference. The whole LG4 exhaust system is a restriction, and the cat isn't the main culprit. Fix the rest of it, and then the cat would be a restriction - but if you fix the rest of it, you'd be motivated to fix the cat, anyway.

 

do it i hate cats i rip all mine off, youll gain anywhere from 5-15hp plus your exhaust will sound a lot better. plus its worth about 40-80 bucks at a scrap yard

 

They are worth some bucks in scrap. I guss with that old of a car it would be fine.. I took the car of my 94 maro and it ran like sheit.

 

o well i got my friends old 1983 cat and gutted it and put a 2.5in pipe through it. Came out good. Looks stock, sorta. I haven't gotten around to the rest of the exhaust yet, and kinda felt like putting my awesome straight piped cat on. Ill probably just wait then. I heard that these brick cats are really restrictive so i thought i may get some power.

another question: what do you call just the section of exhuast between the cat and the muffler?

 

The intermediate or "I-pipe", typically.

 

Like Five7 said... it's not gonna do jack for you with a stock exhaust system in place... you'd have to replace the rest of the system with high flow components for the stock cat to be a restriction.

Once you do replace it, you can get a high flow cat that will barely hinder your performance (sell the old one for scrap for ~$40 and buy a universal cat for ~$60, the net cost is minimal) and you can have the satisfaction of running a clean hot-rod.

 

yea man i cut mine out and welded a pipe in its place for about a week, and there was definitly no power gain, if anything it was slower.about a week later i bought a magnaflow cat and it didnt cut the sou nd down or anything. morale of the story is dont chop it off just replace it with a high flow cat.

 

I really see no point at all to take out the converter on a stock exhaust. I agree with what other people have said...Is it worth the time? I think not. Lets say it does give you 5hp....can you really tell a difference in 5hp?

 

as an avid cat hater, even I would leave it on in this case unless it was PLUGGED or you were just that desperate for scrap money. If you were gonna run 3" cat back then id for sure cut it off. Not worth your time if your gonna leave stock exhaust on

 

Yea man I didn't notice a difference when I took my cat off and put a test pipe on. I have just a stock 2 1/4 piping. No cat, no muffler. The only difference I noticed is the sound.....And the occasional Code 32 when my SES light comes on.

 

code 32 thats egr IIRC

 

Yea I know its EGR. And my EGR valve was fine until I took off the cat. Not enough back pressure I suppose.

 

id just take the egr off then too and the air pump if you still got it connected

 

yea I just recently took the air pump off. Im thinking its just a stored code because the car is running just as good as it was before i ditched the cat. Ill unplug my battery and see if that will erase it. Hope so.

 

well it will definetly erase it if you unplug the battery, now if it comes back then you know you might have a problem. if the car runs fine then i wouldnt even worry about it tho

 

TBI engines need the backpressure from the cat to open the EGR valve, because of the way their EGR valve works. Without it, you will get constant SES lights for code 32/EGR. TPI EGR valves work different and dont have that problem.

 

Ahh ok. Well in about a week Im getting some 3" exhaust with a hi flow cat and a dynomax bullet muffler, do you still think it will come on then?

 

I wouldnt even bother with the high flow cat unless you had to pass smog which sounds like you dont (course someones gonna say federal this blah blah) but to each his own. But that would provide even less backpressure b/c of a better flowing exhaust system, and that of course means more power and according to the other post, more code 32's. I would just take the EGR off and might as well put some headers on there if your doing exhaust anyway.

 

Im gonna wait until I do my 350 swap before I put headers on. Kind of pointless putting them a 305. Espically a stock 305.

 

yeah but if you get the headers now all youd have to do is drop your motor right in since your gonna be getting your exhaust done anyways, up to u tho

 

if you have to pass emissions then throw a high flow cat on there, otherwise I agree with others and say its not worth the time

 

i cut my cat out just because it was rotting out and didnt want it to fall off as i was driving. I could tell the car accelerated a lil better and sounded better, but im going to put a high flow cat on. but i got 65 bucks out of the cat at the yard. gas money for me!