Cat Replacement

Hey Doc (or anyone with knowledge of this) I need to reaplce the cats on my truck (99 Silvy 5.3l) and have heard from a few sources that there is an issue with using aftermarket "hi flo" cats on some of the
newer trucks.
I have talked to both Magnaflow and Dynomax and they claim to have never heard of this.
You know anything about it?
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It has to do with the food ya feed the little dicken's. Have ya tried Purina kitty chow? Less fiber less flow!! <GBMFG>
Sorry Larry, but I knew you wouldn't be expecting it.<BFG>
Roy
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If anybody knew anything about food, it'd be ole Roy. The amount of food he can consume is amazing!!!
Other than that, I imagine ole Snowy will chime in with putting some different gears in it..
Denny
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Yup, and you get to pay for the meal.

No way will he say that. Hell last time a girl needed a speed senser and the idiot's advice was to trade the truck. This time with cat's gone he will advise junking it.
Roy

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Two weeks pay worth of White Castles and if you talk real nice I'll even spring for some cheese sticks..
Denny
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Such a child, last time she had a long list of trouble, a deployed spouse and no way to fix it herself. I suggested too stop the blood loss based on track record while you as usual said to keep pouring money into it (not yours though) Maybe you can pay her dealer bills too. ----------------- TheSnoMan.com
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wrote:

Her long list of trouble was: "The ABS light is on, the brake light is on, and now the speedometer is going crazy." Anybody with a once of experience would pick up on a speed senser failure. You being the fountain of mis information told her to trade the truck! Further you said, let me quote you " It will not be cheap to troubleshoot or repair at a dealer". A couple of people that work at dealers have said it would cost in the area of $100.00 to repair. Your as usual BS answer is not really what a person needs to hear when dealing with the strain of a spouse deployed. But you can't seem to help yourself can ya?

You made your suggestion because you are a idiot. Talk about spending her money. I guess it is more cost effective to trade a truck than it is to spend a $100.00 or so.

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You should really stick to cat food as it is more within your knowledge limitations and likely challanging enough for you as well. You are real trip! I must make you feel REALLY insecure Roy. Knock yourself out and keep up the steady flow of tripe because myself and others find it entertaining at times to make a fool of yourself. ----------------- TheSnoMan.com
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wrote:

I find it odd that you don't disagree with my previos post. Guess that I should take that as a "Ya caught me again Roy, I'm still doing what I do best, BS'ing everybody".
As I told you months ago, I find that a lot of your post's are misleading, wrong and at times, if acted upon, dangerous. Further I said I would be around to point out your BS. You'll note that ya don't hear from me on the few occasions when ya get lucky and make the right guess. What you and other's find entertaining matter's not. I think we really know who has been making a fool of themselves.
Let me adjust your sig for ya.

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Well, see, I thought about feeding it White Castle, but I like my truck!
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Hi Flow CATS are greatly over rated. They are in line with K&N filters promising you the sun, moon and stars in performance gains that simply are not there. People want to believe in them though and shell out big bucks for the state of mind it promotes. The reality is that stock CATS flow well today and as a engine ships it is tuned for intake to exhuast for best power and responce and when you start chopping and hacking you change that and destroy lower RPM responce and power. The problem is that the valve timing in the engine is fixed and the exhaust and intake is designed with this in mind and on the exhaust side to prevent gas pressure from blowing down too quickly during exhaust cycle and coupling more of the energy from the expanding gasses to the crank. (this it what drives the motor) Getting the gas out of cylinder quicker may help at 4000 RPM ormore but not at 3000 RPM and below and actually reduces power output but there will be those that believe otherwise and are smarter than those that built the vehicle. Unlike some others that come here to poke fun or cause problems I do it to help and I have a engineering background in mechanical and electrical engineering too. I even studied IC engine design theory in college many years ago and wrote a few papers on it. Granted the controls on engines have changed since then but the theories they operate on have not. Just like the "law" of insecure posters causing problems to get their kicks or fixes still applies today as well.
----------------- TheSnoMan.com
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If I didn't know about and have read all the B.S. advice you have given to people in AADT, I MIGHT have thought about some of what you have said, but, I am not an inexperienced female who's husband is deployed. As to the flow of a stock cat to a so called hi flow cat, in the case of must trucks yes the stock cats flow about the same as the aftermarket cats, however, this IS NOT the same rule when you apply it to cars.
As to price, you do the math, factory replacement Y-pipe assembly as that is the only way I can buy it will cost me about 1200 bucks, a replacement cat (ONLY the cat) from Magnaflow will cost me 56 bucks each and I can replace them myself.
As to your comment on reducing lower RPM response by "cutting and chopping" please explain to me, why it is that replacing and H-pipe assembly, off of lets say a late 80's early 90's Mustang, with an "Offroad" H-pipe assembly in fact INCREASES the low end response? Oh, please don't tell me it doesn't and try to feed me a lot of B.S. because I know for fact it does because I had an 87 Mustang GT and did just that, with dyno testing before and after.
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YOu are free to believe what you want but a lot of those that squeal the most are really full of it. I use the physics of it which escapes most of the squealers. Consider this (though you seem to have made up your mind) if these magic exhaust system mods worked so great (along with magic air filters) to improve power and MPG why do they not come with them duh.... Detriot is under a LOT of pressure for best performance and MPG on some models and they would do that if it was real. BTW when you consider power curve you also have to look at not just WOT because I do not know about you but I do not drive foot to floor or anywhere near that and a lot of people do not either and engines are tuned with that in mind. Also you should know that all EPA MPG test are conducted with 93 octane fuel not 87 (been that way for many years) and they would not do that either unless it had merit. Sure it will tolerate 87 octane (that is the ONLY reason there is a knock sensor) but that it. 87 octane hurts you more than you know especailly on a hot day unless you beleive that retarding spark a lot has not effect on power output or over all efficency. Octane requirement are not constant and less is needed in cold weather and more in hot weather but most do not realize that and stive to buy the cheapest gas they can find. I have a old 89 4x4 burb that I bought new that gets a honest 18 MPG on highway and will go 600 miles on its 40 gallon tank with some reserve. It does not have a chip or aftermarket intake or high flow cat. It has OEM CAT on it still after 180K miles and a single 3 inch exhaust with a quiet flow master (I forget part number because it has been on there 8 years now) I do run basicall83 octane in it year round and run more than stock timing. It was a super slug when new on a hot day with 87 in it and 93 octane with advanced timing made it a whole new animal that still easily passed Echeck for 10 years until they stopped doing it. ----------------- TheSnoMan.com
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Blah Blah Blah! Once again, you DID NOT even come close to answering my question, but why should I be shocked? I don't want a damn lecture about how an exhaust system works, I want an answer to my question, which I was explicit with what I was asking and looking for.
The point you fail to see is that it is not a question about the comarision of hi flo cats compared to OE cats, it is SPECIFICALLY about aftermarket cats being used on the newer Chevy/GMC trucks.
So, do me a favor, DO NOT reply to my questions if you CAN NOT answer them! Hell you still have to tell us where the knock sensor on the V-10 dodge is.
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wrote:

Yup. The dyno tester just put down a bunch of numbers on a piece of paper. Pure hogwash, right? Why don't you quite giving everybody a snowjob!
I use the physics of it which escapes

Greater MPG means more $$$$$$$$$$$$$$$$$ that consumers are not willing to pay, not until another energy crisis like the one that fueled the present MPG ratings and fleet requirements. Even back then people were complaining both about the low MPG **AND** the cost to achieve higher MPG. If you look at the high MPG vehicles you will notice many of them have "Magic" headers because they WORK! Many of them have lots of "magic" goodies and skimp on the luxuries. MPG costs money that manufacturers are not willing to spend without charging the customer and the average customer is not willing to pay for it so it doesn't get on the vehicles.
Mike D.
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Oh yeah, I almost forgot to thank you for NOT answering my question. I did not ask for a teaching of cat and how they are suppose to work, or any of that. I asked for specific knowledge pertaining to the use of aftermarket cats on newer Chevy/GMC trucks and them causing problems.
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wrote:

Maybe here is a good place to explain the V10 knock sensor.

Yada, yada, When I read your BS, my degree in proctology is needed.

Kinda like the "law" of habitual BS'ers like yourself.

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wrote:

Plese cite the publications so we can learn how to BS like you do!

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You cannot replace them unless the vehicle has a minimum number of miles or past a certain age. I don't recall the age at all, something like 5 years old? Anything directly related to emissions are under more strict government regulations. Also, some emissions parts have a much higher warranty per government regulations. Check with your dealer. However, you said you need to change them. Why? Rusted through or failed? In that case you are free to change them out with aftermarket, high flow or normal, your choice.
Heard this from a parts store clerk when I noticed them in a catalog and said something about them. I would suspect that the newer cats are much better than the original ones and that the high flow ones are not much better than stock, but are definately MUCH cheaper and not much more than standard replacement ones.

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