1999 Silverado/Sierra--Dual Exhaust questions

obeardenobearden Member Posts: 34
edited March 2014 in Chevrolet
I'm considering adding dual exhaust to my
Silverado 5.3 V8 Long Bed Regular cab. I've seen
several trucks that have had this done. The 5.3
sounds great but my main interest is increased fuel
mileage. I regularly drive this truck above 80 mph
for extended periods. Am wondering if anyone has
actual before/after information. This truck has two
catalytic converters and it's therefore a breeze
to add true duals.

Any info would be greatly appreciated


  • bergeronbergeron Member Posts: 6
    I am interested in doing this also. Does adding dual exhaust void any of the Chevrolet warranties?
  • obeardenobearden Member Posts: 34
    Come one folks, surely there is someone out there who has already tried duals on this truck and can give us some real input-actual numbers-as to how it affected fuel mileage and performance. Those of you who are really interested in this-post a message about this topic in some of the other truck topics that you visit.
  • teaboy022teaboy022 Member Posts: 59
    Hey All

    I should be getting my 2000 Silverado Reg Cab Sportside 4.8 In about 5 weeks...

    Im going to hook up a dual exhaust system on it as soon as it comes in..

    Basically what they do is just cut the two pipes leading into the huge GM muffler and put on two flowmaster mufflers with 2 1/2 inch chrome tip tail pipes.

    This will not void your warranty from what i heard.. now if your talking about headers also ... then yes.

    I heard that their is supposed to be a 10-20 hp increase when doing this...
  • mfreeman1mfreeman1 Member Posts: 13
    Your warranty is only void on the new parts and the part you cut(i.e., GM is not going to warrant parts that it didn't make or that you have modified) Everything else is still under warranty. Same with the headers. Of course if you get an exhaust leak after you put in the headers don't expect them to cover it through warranty, but if your O2 sensor goes out, they should cover it.

    Of course that is what your rights are it doesn't mean the dealer won't try to tell you that you voided your warranty on other parts.

  • dallisdallis Member Posts: 8
    edelbrock now has complete kits out for 99&up silverados check them out @ www.edelbrock.com
  • zbad71zbad71 Member Posts: 226

    you are exactly correct. the massey vs ferguson act states that your warranty can not be voided unless the aftermarket part that was replaced can be proven to have caused the failure of the warranted part. and of course, whatever parts are replaced will now no longer be convered under warranty.

    My dealer pulls this every time I am in there. I promptly shut their sewer hole by stating my rights under this act. Its a CYA on their part and so I CYA mine with the massey vs. ferguson act.

    Tee heee heee!
  • madhatteraamadhatteraa Member Posts: 1
    There is a federal law that states any aftermarket products added to your vehicle cannot void your warr. Have looked at many aftermarket cat-back exhaust systems and heve decided on Gibson. All stainless, am going to include their headers (due out soon). They say an increase of about 60 horses, more touque and better milage. Check the different manufactures internet sites for more details (alot out there). I wouldn't use dual exhaust out the rear if your going to be doing any towing. Good luck.
  • swobigswobig Member Posts: 634
    Was reading one of your post on another topic and saw you have a Magnaflow exhaust. I get my Y2K Sierra in Dec. and want duals for performance, but don't want a whole lot of noise (a little rumble would be nice) because my wife would shoot me. Sounds like you did some homework. Could you help me out and recommend a exhaust with medium to low noise and lots of power. I've heard that you can get 10-15% more horsepower out of the engine. Anyone done any dyno test or have any real world experience with it?? Thanks for the help!!!
  • zbad71zbad71 Member Posts: 226
    The most performance for the money would be in my opinion 1st. Jardine 2nd Gibson. 3rd. Flowmaster

    You will get very mild tones from Gibson. Jardine, I am not sure about sound tones. Flowmaster, if you want low to mid noise, I would go with the 70 series.

    If I were most concerned about performance, I would go with Gibson. Gibson's catbacks are rated very high, but don't offer much sound improvement.

    I chose the Magnaflow because it offers good performance increases and a VERY SERIOUS tone as well.
  • swobigswobig Member Posts: 634
    Thanks for the advice. I've heard of flowmaster before, but haven't heard of the others. Not knowing a whole lot about exhaust systems I'm curious about Gibson. Are they very popular, would a bigger exhuast shop have them (or are the special orders), where would I get one, cost?? I'll do some looking on the net, but any advice would be appreciated. Thanks again Dan...
  • zbad71zbad71 Member Posts: 226
    My best advice is to shop around if you want the Gibson. Gibson offers the most torque increase for the money but they still are not cheap by comparison. A catback system (varies on type) could run as much as $300. It is a complete kit though with the hangers and clamps to install yourself. I am not sure what a Gibson muffler would cost by itself either. Another reason I went with the Magnaflow is that the custom muffler shop I went to has them on hand (no ordering) carries a lifetime warranty (even normal wear out) and it is all done local. Most of the catbacks like the Gibson is usually a mail order item and if you have problems with it, you must send it back to the manufacturer, which also means taking it off the truck to send it in.

    Gibsons website is www.gibsonperformance.com
    Flowmasters website is www.flowmastermufflers.com

    Gibsons site has wav files of recorded trucks with the gibson catbacks installed. Unfortunately they are recorded on Ford F150 trucks so it won't be exactly the same exhaust notes as would be on a Silverado.
  • swobigswobig Member Posts: 634
    I checked out the Gibson site and there system is a do it yourself 1/2 day one man type installiation. I would like to do it myself, but I'm a little unsure about the company. Sounds like the have a good warranty, but still have a little doubt. I noticed on the 99's and 00's that they have 2 cats that feed into a pipe then go into one muffler almost begging to be upgraded. I imagine they cut the exhust before it goes into the single pipe and put a better system on. They didn't just cut the single pipe before it goes into the muffler did they?? Wonder how the Gibson system does it. I'll give them a call. Thanks again..
  • zbad71zbad71 Member Posts: 226
    They can split the two pipes and do a "true dual" having a pipe and muffler off of each cat. I would not recommend this on these new Silverados. Too many people I have conversed with have told me that too much low end torque is lost. Actually the torque isn't lost. The torque is moved higher in the rpm band. Unfortunately, that is undesirable on these trucks, especially if you do a lot of heavy towing.

    My exhaust is a single 3" pipe in to a 2 chamber Magnaflow muffler, then 2.5" dual pipe out the back for better scavenging effects. Ends with 3.5" Stainless Steel Slash Cut Tips.

    My best advice is not to go with a true dual. Nobody I know that has done it was at all satisfied and went back to a single in dual out.
    The cats limit most of the flow anyway. Pretty much, after the cat is just a sound preference. Not much is able to be gained in exhaust mods on these new trucks compared to the good years of more lenient emission laws.
  • dave40dave40 Member Posts: 582
    I have dual 40 Series 2- chamber Flowmasters on my 99 Sierra 6.0 no problems here

  • zbad71zbad71 Member Posts: 226
    I was speaking of the 1/2 tons. You wont notice the loss as much with the 6.0l. I still wouldn't do a true dual on the 6.0l either. You may not notice the low end loss, but its a proven fact that it will occur. Not usually noticeable until towing a heavy load.
  • swobigswobig Member Posts: 634
    Thanks for the tip. I'm still a little confused on the difference between 2 and 3 chamber mufflers though. Is it sound, performance, outlets that make it a 2 or 3 chamber?? I've also heard 10-15% increase in horsepower. With 285 stock this would translate into a increase of about 35 horse. Does this seem right?? What kind of increase do you think you got out of your exhaust system?? Take care..
  • zbad71zbad71 Member Posts: 226
    The difference in chambers are primarily sound. A 3 chamber may have a little more backpressure than a 2 chamber, but if so, not much. The two chamber has two sound deadening chambers or baffles. The 3 chamber has 3.

    Some mufflers use fibers to quiet down a muffler, some use strictly chambers like the flowmaster. Some use both.

    A 2 chamber will be louder interior and and exterior than a 3 chamber. Some say that the 3 chamber mufflers are just as loud exterior wise, but less interior resonance. I did not find that to be true in my case, but it may just be a difference in muffler types or a difference in how other people interpret interior resonance, etc.

    I think 35 hp is wishful thinking on these new trucks. The catalytic converters are the biggest restriction in flow. Even using a freer flowing catback exhaust will most likely not gain 35 hp on a stock truck. Maybe in the higher hp "built" motors. The more of other mods that you do, the more gain you may see from the catback.

    More realistically, I would say you might gain 20 hp and around 15 lbs torque.
  • jerobbinsjerobbins Member Posts: 48
    I'm interested in a horsepower and torque increase (of course), but what I would really like is to save gas. When I get a truck I'll be driving it over 80 miles every day - even a single mpg saved will add up. Do any of the exhaust systems help the fuel economy?
  • swobigswobig Member Posts: 634
    from a friend that has a cat-back system that he's gained about 1-2 mpg. I too drive 80 miles to work and would like to save a few bucks. Zbad71 probably knows a little more about that though.

    Hey Zbad71 you've made a few, how should I say, "friends" on some of the other post. Hang in there! Thanks for the help..
  • zbad71zbad71 Member Posts: 226
    Yeah, its hard to be humble around here. I am trying to "get along", but people just take things so personally.

    I think you will get "some" level of fuel economy increase with all exhaust mods. As long as you don't expect miracles, you will be satisfied. I picked up 1-2 mpg increase with the exhaust I went with. Some of that may be from it getting more and more broke in though too. I would say 1 mpg is a "safe" assumption for a catback mod on these new trucks.

    Take care.

    Did I say anything that would offend? I have to second guess everything around here to make sure.
  • swobigswobig Member Posts: 634
    Your doing just fine...
  • swobigswobig Member Posts: 634
    just ripped off his exhaust and put in a new system. Took the cats off and put on glass packs - says it made a hugh difference. Would you do this to a new truck?? Not worried so much about emmissions, only power and engine longevity...
  • zbad71zbad71 Member Posts: 226
    No. I wouldn't. I don't think any of the 50 states will pass the inspection on it without cats. Not to mention I am surprised the computer is not throwing codes hand over fist. The O2 sensors and all that emission crap continually monitors that stuff. Your friend must of "tricked" the computer emission components or taken all the emissions stuff completely off. Either way, he or she will have an extremely tough time getting an inspection sticker.

    Since the cats are most of the restriction of the exhaust system, I can see where some significant gain would be had. However, by removing the cats, it may affect the scavenging effect of the system and could "reduce" torque and hp in the low end.

    In my opinion, its always risky messing with emissions, both with the law and with possible problems it could cause with the vehicles driveability. However, I have heard others who have done it, so there must be a way around both the aforementioned.

    Take care.
  • swobigswobig Member Posts: 634
    but as far as I know, he cut the old stuff off and just put on the new stuff. I'll have to ask if he did any computer fixes. I know he hasn't had any problem (fail codes), so maybe he did do something. Wisconsin does not require a inspection sticker so it's pretty easy to get away with. I don't think Illinois does either, must be just a handful of states. But I would definatly keep the cats if I did take them off - still thinking about it - hate to give up that stainless steel....
  • bob259bob259 Member Posts: 280
    I have a 1999 5.3 Silverado and chose the Borla dual rear exit for my truck. Had Gibson on my last truck and while the sound was great the way this Borla fit made me a convert forever. I also have less cab noise and droning at part throttle than with the Gibson. Here in the NE the Stainless Steel Borla should last a lot longer, while I know Gibson now offers it I still feel the Borla is a better buy after having and installing both. In addition, after two years on my last truck the Gibson was starting to show rust, and I was told last week by the dealer the person that bought it had to have a new exhaust put on due to rusted out tailpipe and exit flange on the muffler.
  • bob259bob259 Member Posts: 280
    Another quick note, on both vehicles I had to do NO modifications to the computer. Performance, it was a noticeable difference in the seat of the pants feel between the stock and Cat back replacements. I don't think it was as high a HP increase as they like to quote, unless you looking at WOT (wide open throttle) spec.s, day to day driving it's noticeable but doesn't turn your stock truck in to a racer by any means.
  • bob259bob259 Member Posts: 280
    As mentioned by another reader taking the converter off is a no no and will cause him problems in any of the new state emission test. Today's motors run better with a little back pressure, so his comparison my well be short lived and he will no doubt end up with valve problems and diminished performance down the road. The old school, and in all but race motors was bigger is better, today it is smaller will give you more torque, better gas mileage and more power with your street motor.
  • swobigswobig Member Posts: 634
    that he ripped the cats and exhaust. I'm getting a 2000 Sierra and after thinking about it a little, I think I'll leave the cats alone and just go with a better muffler. I'll sleep a little better at night. If the darn thing would only get here!!!
  • rubluetoorubluetoo Member Posts: 175
    How does the borla sound? And what is the price?
  • bob259bob259 Member Posts: 280
    The Borla sounds good, not to loud like a Gibson but a deep sound. A nice middle between stock and the louder Gibson. If I remember the price was $525. delivered through Summit.
  • billk5billk5 Member Posts: 14
    What did you get for that kind of money, did you install yourself?
  • bob259bob259 Member Posts: 280
    Typical CAT back exhaust, stainless steel with split rear exit, including tips. Yes I installed it myself. It is a real straight forward install and with a floor jack and jack stands anyone can do. I believe it took me less than a hour all together to do. (However, I had installed a Gibson on my earlier truck so I had an idea of what was needed)
  • billk5billk5 Member Posts: 14
    Does this system use a single muffler ? Do they sell through a store or only mail order ?
  • bob259bob259 Member Posts: 280
    It uses a single stainless steel muffler, 1 inlet and two exit points. Not sure where your located so it would depend. I purchased mine mail order because it ended up costing less then a local custom shop. If you have any local Truck, Custom, Cap/Accessories, Speed shops in your area they may have one in stock. If not I would highly recommend Summit Racing in Ohio, fast service, fair prices and free shipping.
  • powerisfunpowerisfun Member Posts: 358
    I also recommend Summit Racing. In addition to the great service, good prices, and no shipping charge mentioned above, they also have a very good tech department if you have questions. I had a question about a part I was thinking of buying and their tech department was very helpful and seemed to know my vehicle better than I did (and I know it pretty well!). JCWhitney is also very good, and if you can get a catalog with the 15% discount coupon/code on it, their prices are better than Summit's (even with shipping charges).
    Summit has better selection, though, so if you're looking for a specific racing part, they're the better bet. For the Borla exhaust, I'd go with JCWhitney if you can get the 15% off (I can give you my catalog's 15% off code and part number if you like, but it expires on Dec. 31st which may be sooner than you were planning on buying). At $600 catalog list price, you'd save $90. JCW also carries Gibson exhaust, which are not stainless, but they're aluminized and they cost only about $300.
  • pyrodexpyrodex Member Posts: 47
    I have had experience with Borla's products in the past on both cars and trucks. They ARE the best in my opinion. Not cheap...but darn good. They sound great, too. www.borla.com
    I think Performance Products sells Borla exhausts too but it's been a while since I was in the market.
  • leathal02leathal02 Member Posts: 114
    i went to a local exhaust dealer, and he quoted me a price of alittle over $300 for a flowmaster with dual exit

    is this good for a custom job??
  • dave40dave40 Member Posts: 582
    Sounds about right
  • cgaule1cgaule1 Member Posts: 1
    I have a 99 Silverado Ext.Cab. The local exhaust shop put on a single Vortex glass pack with 3" pipe after the Y and chrome tips. Sounds great,feels like it has a little more pep. Not sure on mileage yet,just got it done Friday the 5th. Paid $237 for it.
  • powerisfunpowerisfun Member Posts: 358
    Just thought I would repeat this from the "Headers on late model trucks" topic, since it's related to performance exhaust:

    If you have a '99/'00 Silverado/Sierra, I don't
    think I'd bother getting shorty headers. In one of the articles on the JBA Racing page (http://www.jbaracing.com ), it shows a picture of the stock exhaust manifold removed from a 5.3L engine and it looks very unrestrictive (a lot less restrictive and better designed than the stock manifold of my Vortec 5.7L). It looks like a well designed manifold and resembles a shorty header already, so it probably has the similar siphoning (i.e. scavenging)
    characteristics. This was probably one of the important ways that GM got the power up on these new engines (Good show GM!). Unless you can find a set of smog-legal long tube headers (lots of luck there!), or you just want the look of chrome headers in your engine compartment, I wouldn't waste the money.

  • dave40dave40 Member Posts: 582
    Long tube headers work best for engines over 500hp....
    If you got to have em Arizona Speed & Marine has them for the new Silverados... starting at $800.00 I'am happy with my JBA shorties...$400.00
    Awesome Dave-40 Commander In Chief/U.S.TruckForce
  • powerisfunpowerisfun Member Posts: 358
    "Long tube headers work best for engines over 500hp..."

    I've heard that too, but according to the JBA website, long tubes increase torque in the lower rpm range which would seem to be more to a truck-owner's liking. The "Chevrolet SysteMax" article shows that the long tubes increase low-end torque better than the shorties. The engine they tested is a Target Master Chevy 350 with first ~370 hp and then after increasing the compression ratio ~400 hp. Understandably that is still a relatively high horsepower engine, but it's less than 100 hp more than the GM 6.0L.

    Anyway, I ended up getting Flowtech brand headers for my 5.7L and they're great. Definitely more power especially in the 2400 rpm and higher range.
    About the same (or at least less noticeable) at lower rpms.
  • epoeepoe Member Posts: 56
    I think there's something to be said with not using a true duel system. you can cut the cost i belive and use 1 cat and split after that like the corvettes are setup and tuned.. I don't thing they removed the true duel because it is cheaper but it's said that having the flow in harmony with both sides or all 8 cylinders performs better.
  • leathal02leathal02 Member Posts: 114
    that it is better to leave the cats the same as they are and just put a different muffler on it. I think that flowmaster said this. They said that if you make it a true dual exhaust( a muffler for each header or whatever) it will lessin the back pressure taking away low end torque. It sounds pretty accurate to me, but I am not sure.
    Im just going to Y into a flow and dual out of that, making my nice low end sound and hopefully gaining some power and maybe if i stretch it enough maybe even some gas mileage...
  • artpartp Member Posts: 156
    Don't the manufactures just put a real nice exhaust on from the factory? I wouldn't think it would cost much, if any extra.
  • powerisfunpowerisfun Member Posts: 358
    The only thing I can come up with is that they have to make the best all-around truck. Meaning that they have to make a truck that has the most mass appeal. For most people a quiet exhaust is very desireable. Since a quiet exhaust is also cheaper (single muffler, single tailpipe, one piece design, etc.) they have to weigh the cost effectiveness of offering a performance version. Most people don't want to pay the extra price for headers so the cost effectiveness of offering them as an option is not there. Whether this is the real reason is just a guess, but it's the best I could come up with.
    One other guess is a bit more cynical. Is it possible that the manufacturers and the after-market folk are washing each other's backs?

    P.S. I just added a cat-back exhaust to my truck and you can read about it in topic #1214 "Headers on late model trucks". It's a '98, but the exhaust set up is very similar (if not a direct carryover) to the new trucks.
  • artpartp Member Posts: 156
    I've heard that modifying the existing exhaust can change the back flow, therefore causing the computer to change air/fuel seetings to try and compensate. Any comment?
  • m1685m1685 Member Posts: 71
    I thought the catalytic converter did the emissions, not the mufler. All a performance muffler does is let more airflow out. It still has to go through the cat.
  • big_jbig_j Member Posts: 1
    How does adding a high performance exhaust effect emissions. I have a '99 Silverado and live in New York State where they do emissions testing. Could installing a Borla-type system possibly cause me to fail the emissions tests??
  • powerisfunpowerisfun Member Posts: 358
    I guess a cat-back exhaust could affect emissions if it drastically changes the temperature profile of the exhaust as it exits. A lower (or higher temperature) could cause certain chemical reactions to occur (or prevent the correct ones from occuring). Most cat-back exhausts have CARB (smog-legal) approval, and I'm sure Borla does, so emissions shouldn't be a problem there.
    Headers definitely do affect emissions because their sole purpose is to scavenge (i.e. like a siphon effect) more exhaust from the cylinder (so exhaust is not only being pushed out but pulled out as well). Shorty headers are one of the smog-legal varieties and they're probably only effective if your manifold is not well designed (e.g. the manifolds on a chevy 350 are both restrictive and horizontal for very little scavenging, however the new GM Vortecs' manifolds look very well designed and headers would probably be less effective there).
This discussion has been closed.