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Posted: 4/14/2002 4:58:32 PM EDT
...is illegal on street vehicles, etc. I know this- please save your legal advice. The question is: will my '93 Chevy Suburban (5.7L) benefit from this little procedure or not? I have heard that hollowing it out causes pressure to build-up in the empty chamber, and can cause problems at higher rpm's. I am dying here on mileage, even with a tune-up, and I will be getting a cat-back exhaust system later, but I need to reduce the restrictions on my exhaust system. Will it help my power and mileage, and if so, does anyone know how the hollowing can be accomplished? FYI: the vehicle is not subject to emissions testing and inspections, but that's another story. Removing the entire cat is not an option because of other reasons. Anyone have any opinions or advice on this procedure?
Link Posted: 4/14/2002 5:04:37 PM EDT
[Last Edit: 4/14/2002 5:06:07 PM EDT by quietshoez]
i have heard that some very bad people have broken the law by removing it altogether and putting a straight flex exhaust pipe where the conv. used to be, and i guess this would work, but i wouldn't know.( i heard that they placed the shell of the converter over the top of the flex pipe to conceal this illegal act, but this may be a myth also.
Link Posted: 4/14/2002 5:08:42 PM EDT
Link Posted: 4/14/2002 5:17:33 PM EDT
That's right... if you can take it off without any damage (i.e. cut the bolts with a grinder or something), ram a steel bar thru it to break out the catalyst so it won't clog the system and re-install... what happens when they go bad is that the core breaks up and clogs up the exit or the muffler, effectively creating so much backpressure that the engine will no longer run. The exhaust gasses need to go somewhere! Just be sure you get all that honeycomb stuff out and it should run ok. (DISCLAIMER: not that I've ever done this before...) FITTER out
Link Posted: 4/14/2002 5:21:39 PM EDT
what quietshoez said shocks my virgin eyes...I hope this never accidentally happens to my truck! I guess it all depends upon whether this accident can take place without welding or expensive tools. Otherwise, muffler shops can get fined $10k for this little accident. Still searching the web for a link to "how to."
Link Posted: 4/14/2002 5:25:29 PM EDT
I think you're better off with a free flowing cat, as opposed to a "test tube." Comercial cars aren't ment to have open exhausts. My Camaro's gas milage and power acyually dropped with an open header system.
Link Posted: 4/14/2002 5:26:28 PM EDT
Link Posted: 4/14/2002 5:27:22 PM EDT
Originally Posted By dissipator556: what quietshoez said shocks my virgin eyes...I hope this never accidentally happens to my truck! I guess it all depends upon whether this accident can take place without welding or expensive tools. Otherwise, muffler shops can get fined $10k for this little accident. Still searching the web for a link to "how to."
View Quote
i read somewhere (in canada or offshore i think) that the convertor can be cut down the seams with a hacksaw,grinder or dremel tool, and reattached together with jb weld, remember, should this accidentally happen, there would be a piece of flex tube (available at any wal-maryt or auto store) inside of the shell so no pressure would be on the shell itself, just the flex pipe. or so i heard.
Link Posted: 4/14/2002 5:34:56 PM EDT
man you guys are more afraid of the smog nazis than you are the gun nazis. but anyways if you don't have too pass smog why not do it I doubt a cop will ever bother you about it they don't want to crawl under you burb. if they do tell them you got all the exhaust work done in TJ mexico. I would run full headers to dual 2 1/4" pipes with a balancer tube and turbo 2's it will sound good and it will breath alot better gas milage should also go up. check out WWW.summitracing.com and order there free catolog.
Link Posted: 4/14/2002 5:35:36 PM EDT
There's always getting a 'low restriction cat converter'. Not sure how much they cost.... might find out online (plenty of places ie JC Whitney) If you happen to have an air compressor, impact (or air ratchet), penetrating oil, hammer (medium size) and the right sockets, removing the pipe after the cat is no problem. Being a 'berb, there should be plenty of crawling room. Any how, if you can leave it parked a while, hit the exhaust U bolts w/ some WD40 or other penetrating fluid. Get some extra exhaust U bolts (clamps) incase they get destroyed. The hammer is used to 'help' remove stobborn pipes. Slide out the cat from the front pipe and inspect. If you happen to have an air tube connected to the cat, remove that too. Remove cat and 'inspect it'. Installation of the new on is in the reverse order.....
Link Posted: 4/14/2002 5:36:34 PM EDT
Oh yeah I have ran cars with nothing more than open headers no pipes or mufflers or cats and it is fun gains you a little power but is loud as hell.
Link Posted: 4/14/2002 6:00:05 PM EDT
Link Posted: 4/14/2002 7:22:58 PM EDT
Thanks guys. TheDave1164- please have yourself a nice hot cup of "shut the fuck up."...jeez, some people are a little TOO paranoid around here- anyone else noticed?
Link Posted: 4/14/2002 9:24:41 PM EDT
Link Posted: 4/14/2002 9:37:37 PM EDT
Ram a pipe down through it & knock the guts out of it... You can do it without removing the converter... Just remove whats behind it... After all the shit is broken up in the case, just fire up the motor and rev it a few times... All the garbage will blow right out the back... (Don't breath the dust either, it is rumored to cause cancer) You're truck will run like a whole 'nuther truck [:D] (Not everyone can afford to replace an expensive "un-needed" part) I don't know this from personal experience, only hearsay.[rolleyes]
Link Posted: 4/14/2002 9:40:06 PM EDT
Dispasstor556, Running free flow through the cat will not increase back breasure, it will decrease it. Your best bet would be to get a high flow cat and change your mufflers to a less restrictive set(flowmaster 3-chamber). By running free flow you will be giving up some low end torque but will gain hp in the higher rpm range. The reduction in torque won't really be noticable unless you tow something extremely heavy, over 3000lbs. If your looking to increase gas mileage check on getting a new set of injectors. They run about $300 and will make a big difference in the way your truck runs. Is your truck a TBI injected, I can't remember when they switched? I had an 89K5 Blazer with no cat and free flow exhaust, the injectors helped the most, you could see the difference looking at the spray of the old and new. Hope this helps. Bill3508
Link Posted: 4/14/2002 9:47:20 PM EDT
Bill: They new engines swithced over in 96. that was the first year for the Vortecs. Also the best flowing heads Chevy ever produced. I agree with the statement about decreesing backpressure will hurt low end torque. U need ot have some pressure, get a free flow cat so there will be something there in place. Hell is this is the original one that came with it, the unit might be backed up anyways and anything new will help it breathe a little better.
Link Posted: 4/14/2002 9:50:20 PM EDT
Originally Posted By dissipator556: ...is illegal on street vehicles, etc. I know this- please save your legal advice. The question is: will my '93 Chevy Suburban (5.7L) benefit from this little procedure or not? I have heard that hollowing it out causes pressure to build-up in the empty chamber, and can cause problems at higher rpm's. I am dying here on mileage, even with a tune-up, and I will be getting a cat-back exhaust system later, but I need to reduce the restrictions on my exhaust system. Will it help my power and mileage, and if so, does anyone know how the hollowing can be accomplished? FYI: the vehicle is not subject to emissions testing and inspections, but that's another story. Removing the entire cat is not an option because of other reasons. Anyone have any opinions or advice on this procedure?
View Quote
Actually, if I remember correctly... Go to an auto parts store, and tell them you have a '93 3500 series truck.... Have them get the exhaust parts book out, and look over the diagrams of the exhaust systems... Some of the H.D. trucks came equipped WITHOUT converters (option "C6P" I think) and used a factory installed straight pipe where the converter went... The rest of the system should be very close to the same... I worked for a Chevy dealer parts dept years ago, and learned this as fact...
Link Posted: 4/14/2002 10:05:32 PM EDT
Just get a free flow cat. I have one on my truck and it works great. It is almost hollow, and cuts down on emissions. You can get the performance you want without violating any laws.
Link Posted: 4/14/2002 11:04:39 PM EDT
I have seen cars with the converter completely removed still pass emissions testing. A good running engine & a recent tune-up apparently will get one by. FYI, there's a "high flow" converter out on the market. I put one on my Toyota 4x4 & it helped it breathe better. I'm sure they're made for Chevy's too.
Link Posted: 4/15/2002 7:02:46 AM EDT
Troy, ordered the catalog- thanks! At the very least, I will be getting a flowmaster 3 chamber exhaust system installed at a local shop. Then, hopefully I will also be getting a hi-flow cat put on, or have the old one modified to breathe properly. Whichever this place will do the cheapest, I suppose.
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