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exhaust bottleneck?

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by tecton, Mar 24, 2003.

  1. tecton

    tecton 1/2 ton status

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    i have dual dynomax exhaust w/headers

    when i drive my blazer, dont get my wrong...the mfer hauls...but it seems like...its holding back?

    im wondering if running pipes directly from my headers out the side behind the doors (no mufflers?) would improve power

    what abuot glasspacks?

    from what i know, exhaust is like an "everyone is special" situation...any kind of exhaust perform for EVERYONE...and is that an upgrade from what i have?
     
  2. 84_Chevy_K10

    84_Chevy_K10 Banned

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    What gears you got?
     
  3. tecton

    tecton 1/2 ton status

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    stock i assume
     
  4. Miller

    Miller Registered Member

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    the exhaust you exsplained is what the 1/4 mile drag guys woul call a normal exhaust. headers with dumped or angled out the sides. but these cars are reving high, they probly use 2500-6500 where as your burb will make power from idle to 4000 if you push it to 4k.

    Im gona guess youve got 350??????? with a 350 Id run a single 3" pipe with good muffler of your choice. with a 454 I might step up to a 3"-2.5 dual tailpipes.

    its all about backpressure, if you have to much its hendering beforemance, if not enough its also hendering.
     
  5. DukeBoy88

    DukeBoy88 1/2 ton status

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    I can't imagine you'd gain much without mufflers. It sounds like you have quality pieces that wouldn't restrict flow. It would deffinatly be louder and might "feel" like more power, but I don't think it would be measurable.
    what size pipes and what type mufflers do you have?
     
  6. sled_dog

    sled_dog 1 ton status

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    Look on your fenderwell data sheet should tell you what gear ratio you have. Maybe that is. If it does then add it to your sig and let us know. I am not understanding this feels like it is holding back. I have 33s that measure 31" tall and 2.73 gears in my K5 and it takes a bit to build speed but after it builds some RPMs(takes a little longer than I like) it rips. I just have manifolds to gutted cats to cherry bomb glasspacks to tail pipes, 2 1/4" the whole way. What Dynomax "exhaust" is this? What mufflers? Pipe sizing? I wouldn't run bigger than 2 1/2" dual exhaust on a burb or blazer unless its big block. And the 2 1/2" I know in my head isn't a great idea and could be losing torque but it looks and osunds good /forums/images/graemlins/wink.gif
     
  7. Thunder

    Thunder 3/4 ton status

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    What do you mean by holding back? Your exhaust sounds fine to me. Are you having problems at higher RPM ?
    If so your ignition is prolly to blame. Stock HEI starts loosing it around 4500 RPM sometimes sooner if parts are wore.
     
  8. jwingfield2k

    jwingfield2k Registered Member

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    Backpressure isnt an issue on that engine, is it?
     
  9. sled_dog

    sled_dog 1 ton status

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    yes it is an issue. a standard size(not stroked or bored) small block shouldn't really have much larger than 2 1/4" exhaust or else the torque will start to fall off thanks to such limited back pressure.
     
  10. Ryan2286

    Ryan2286 Registered Member

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    SO if I'm running stock manifolds with just a Y-pipe, I'm better off than running headers and mufflers performance wise?
     
  11. sled_dog

    sled_dog 1 ton status

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    depends. Mainly on what kind of power you want and some other things. Headers can and often do increase torque, a good say 1 5/8 primay tube header does a good job of increasing torque AND horsepower. However if you just dump out the collectors into 3" glasspacks this isn't efficient. If you however dump into some reducers going to say 2 1/2 or 2 1/4" exhaust with glasspacks and some form of piping(not just header to muffler and thast it) it can be quite efficient. I believe headers will offset the loss of torque when running say 2 1/2" piping. I know I have a friend with a Ford that has the Small Block 5.8L and it came with Headers and 2 1/2" piping to flowmasters. He put cats on it for inspection and swears that when the cats are on(removeable) the truck seems to have a slight bit more torque. But it also acts as a muffler and really reduces his sound. My other friend runs Tri Y headers on an 84 3/4ton Chevy, it dumps into 2 1/2" piping that goes through an H Pipe and then a set of cats, after taht it simply goes out in front of tires and the only mufflers are a set of glasspack tips that don't do an insane amount. They are legal though. Anyway it sounds awesome and he noticed a BIG horesepower and torque gain over the stock manifolds and stock exhaust. Sorry for the length of this I ramble sometimes. If someone feels I am wrong on some points please let me know I am always open to criticism on my ideas.
     
  12. tecton

    tecton 1/2 ton status

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    first gear it feels like loads of power, but i shift out too fast
    second is about the same....loads of power but i shift out too fast
    third just plain sucks
    OD feels like the engine is about to blow, lol

    unless i catch a hill at just the right speed to get that resistance and momentum, ill crawl up it

    i guess i just wont be able to tell for sure until i get a tach put in

    i dunno....its like if your blowing a piece of paper with your mouth...you want to concentrate all the air onto the paper...but with my k5 it feels like some is getting spread out...like its just blowing for nothing
     
  13. sled_dog

    sled_dog 1 ton status

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    thats not exhaust its gear ratio. My truck does that too and I don't have any exhaust bottlenecks just too big a tire for my gears. 2.73s, a weak engine(my old 305), and 31" tall tires was a dog and a half in 3rd and 4th gears(manual). IN fact 4th gear the truck actually slowed down and wouldn't pull over 2000rpms.
     
  14. alec78

    alec78 1/2 ton status

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    A auto tech friend of mine said it best one, "noise does not make power..."

    With dumps or glasspacks the only thing you get is a ringing in you ears after a drive, and eventually lose of hearing (just ask my wife). Glasspacks are actually bad for power, take a look inside one and you'll see why.

    When you get a good muffler, just make sure it holds the ID of the inlet through the whole thing. Quite a few bottle neck once inside the case.
     
  15. sled_dog

    sled_dog 1 ton status

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    yeah I run glasspacks but I also have tubing all the way from my manifolds to the very rear of my truck wiht plenty of bends going over the rear and out the back(never go out the back on a blazer by the way). This makes it much quieter as well as regain the power I might lose. I am going to simply remove my glasspacks and tailpipes and just put flowmasters on with turndowns. Looking for some more noise and who knows maybe a little power.
     

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