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Cut the cats??

This is a discussion on Cut the cats?? within the External Engine forums, part of the LSx Technical Help Section category; I am privileged to live in an area of Tennessee in which I do not have to pass emissions. So, ...

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    Junior Member GungHoPopsicle's Avatar
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    Cut the cats??

    I am privileged to live in an area of Tennessee in which I do not have to pass emissions. So, with that thought, I figured until I put some long-tube headers and throw on a better exhaust, I'd cut off my cats to improve the crappy sound that my Flowmaster (NOT my choice at all...was a Christmas gift and looked/sounded a lot better than the single exit factory exhaust) puts out. However, a Certified Mechanic friend of mine (who used to own/run a performance shop working mainly on Steeda and Saleen Mustangs as well as Corvettes (just so everyone knows he's not a novice)) tells me that, by doing so, there won't be any back pressure thus my valves will burn up.

    Sorry for the overload of parentheses.

    Anyway, he's a really car-savvy guy, always has given me correct information, so I don't really question him on much of anything auto-related because his knowledge most definitely outweighs mine, but...is this true?

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    2004 HEAD/CAM CTS-V 9t8z28's Avatar
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    No Way

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    Junior Member GungHoPopsicle's Avatar
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    Arctic White
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    Quote Originally Posted by 9t8z28 View Post
    No Way
    Are you answering "Should I cut the cats?" or "Is he right?"

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    Pathelogical Liar BlackLT1Z28's Avatar
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    IF he was right, then most of the people on these boards would have burnt valves. Cutting the cats or going with an ORY will not have those effects.
    It might few up a few ponies and change the exhaust note a little.

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    Junior Member GungHoPopsicle's Avatar
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    Arctic White
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    Quote Originally Posted by BlackLT1Z28 View Post
    IF he was right, then most of the people on these boards would have burnt valves.
    That's exactly what I was thinking. If this really was a problem, I assume it would be pretty well-known that you just don't do it, but since I've never heard of that occurring before, I just had to do some research.

    Maybe he's right and it takes a toll on the valves over time, but how long a period of time I don't know.

    I'd like some more answers to this question, however, before I make my decision. Thanks, BlackLT1.

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    Pathelogical Liar BlackLT1Z28's Avatar
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    I don't think it takea a toll on the valves at all. The cat is just a piece in the exhaust system. It really has nothing to do with the valvetrain.

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    2004 HEAD/CAM CTS-V 9t8z28's Avatar
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    what about earlier model cars. they didn't have cats and nothing is wrong with them

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    We'll be back... GatorSS's Avatar
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    Quote Originally Posted by GungHoPopsicle View Post
    ... I figured until I put some long-tube headers and throw on a better exhaust, I'd cut off my cats ... However, a Certified Mechanic friend of mine tells me that, by doing so, there won't be any back pressure thus my valves will burn up.

    ...is this true?


    "Certified Mechanic" doesn't make one a mental giant.

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    Having almost anything in the exhaust, including open headers, provides sufficient back pressure to protect the valves. What kills valves is a setup so short in length that allows cold outside air to get sucked all the way back to the exhaust ports before the next exhaust cycle begins.

    There is some advantage to having a certain amount of back pressure, without it your low end torque can suffer.

    TUNE your exhaust, don't just slap stuff in there because it sounds good to your ear or is promoted by some rave advertisement. A properly tuned exhaust system is perhaps one of the most important components of a high performance engine.

    Anyone remember the old 2-stroke motocross bikes? The ones with expansion chambers? The ones that went "tink tink tink" at idle and really raised heck under power? Classic illustration of engineering in action.

    http://en.wikipedia.org/wiki/Expansion_chamber

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    Junior Member GungHoPopsicle's Avatar
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    "Certified Mechanic" doesn't make one a mental giant.
    Which is why I mentioned that he previously ran a performance garage, not just some mom-and-pop muffler shop. I see you altered my quote to omit that information, however...

    He does, indeed, know a great deal, and I don't intend in anyway to portray him as someone who doesn't (or a "mental giant", for that matter), although I felt this particular subject required more research.

    Upon asking him the question of topic, I posed the question that if, once I applied headers, could I do this? He told me that with short-tubes, yes, but with long-tubes, no. Keep in mind my SS is pretty bone stock with the exception of the hood and exhaust.

    Anyway, thanks for the reply, Steve. I, admittedly and regrettably, didn't really get into autos until maybe 5 or 6 years ago, and even then it wasn't exactly my only point of interest, so I have quite a bit to learn (which is one of the reasons I'm here!). I think it's a common goal for us Camaro owners to shame those 'Stangs out on the road, and it's no secret that they can put out some pretty mean sounds, hence a huge reason for my want to rid my 'Maro of the cats: It'd be nice to shut 'em up once in a while. So, until I pay off a big chunk of this debt I have, I can't exactly go gung-ho into the pricier modification department, and I'd like to have something to tide me over until then. So, with my current set-up, is this a dangerous thing to do (removing the cats) or would you say I have a green light?

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    2004 HEAD/CAM CTS-V 9t8z28's Avatar
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    I had shortys on my 97 with no cats and no problems.

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    Junior Member GungHoPopsicle's Avatar
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    Arctic White
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    I'm gonna do it. I don't see anything wrong with it and no one else here does, so the hell with it. Thanks to everyone who replied.

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    Gold Member BlwnCamaro's Avatar
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    Quote Originally Posted by GungHoPopsicle View Post
    Which is why I mentioned that he previously ran a performance garage, not just some mom-and-pop muffler shop. I see you altered my quote to omit that information, however...

    He does, indeed, know a great deal, and I don't intend in anyway to portray him as someone who doesn't (or a "mental giant", for that matter), although I felt this particular subject required more research.

    Upon asking him the question of topic, I posed the question that if, once I applied headers, could I do this? He told me that with short-tubes, yes, but with long-tubes, no. Keep in mind my SS is pretty bone stock with the exception of the hood and exhaust.

    Anyway, thanks for the reply, Steve. I, admittedly and regrettably, didn't really get into autos until maybe 5 or 6 years ago, and even then it wasn't exactly my only point of interest, so I have quite a bit to learn (which is one of the reasons I'm here!). I think it's a common goal for us Camaro owners to shame those 'Stangs out on the road, and it's no secret that they can put out some pretty mean sounds, hence a huge reason for my want to rid my 'Maro of the cats: It'd be nice to shut 'em up once in a while. So, until I pay off a big chunk of this debt I have, I can't exactly go gung-ho into the pricier modification department, and I'd like to have something to tide me over until then. So, with my current set-up, is this a dangerous thing to do (removing the cats) or would you say I have a green light?
    Yea you could do that without burning the valves for shure. That is one of those old hot rodding myths that running open headers will burn the valves. Like someone stated earlier the danger is sucking cold air back to the valves but with at least manifolds or headers on the engine it's not a problem, maybe if you ran the engine with no headers or manifolds at all it might cause a problem, but with no cats or open headers its not a problem, been running like that for years personally.

  14. #14
    JOSEY FUCKING WALES! Frankthetank's Avatar
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    Pacesetter Long Tubes......Off Road Y Pipe (which means no cats) and Tsp RUmbler Exhaust.....Couldnt be more happy with the sound! Mayb just a bit loud.....but everything runs fine......btw valves are fine too

    TSP Rumbler, LT's, TSP Tqr2, PRC 921 Springs, Comp Lifters, Chromoly 7.4" Pushrods, Titanium Retainers/Seats/Seals, ARP head bolts, BMR full Rear suspension

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    I removed the cat on my 3rg gen and I dont have a problem

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    Member camarolvr69's Avatar
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    frank you got same exhaust setup as me
    i love the way it sounds.... nice and deep and LOUD
    Last edited by camarolvr69; 01-26-2007 at 02:47 PM.

  17. #17
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    I personally didn't notice a ton of difference when i eliminated my cats and still had flowmaster, now when i slapped my loudmouth on, hells yeah!

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