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Does size really matter

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by husurddy, Aug 9, 2001.

  1. husurddy

    husurddy 1/2 ton status

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    I posted the other day about finding a brand new set of Thorley tri-y's for a hundred bucks. After checking the part numbers and reading the posts I bought them. I did a search here on exhaust diameter and there seems to be a debate on crossover or not, and 2 1/4 or 2 1/2 inch in relation to torque and back pressure. This is for my driver and I will running duals, but still want to squeeze every bit of torque out I can. Any help will be greatly appreciated.
     
  2. solowookie

    solowookie 1/2 ton status

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    from what I understand if you engine is basically stock with no serious mods then you definately be better off with a 2 1/4" pipe. the smaller the pipe, the higher the torque, and the larger the pipe the more the hp.

    I gotta stock setup with true duals, and long headers. it made a HUGH difference, but I went 2 1/2. if I had it to do all over again I would definately go with a 2 1/4" though for the added torque.

    also, if you are doing a good exhaust I think you'd also benefit from a K&N filter.

    <font color=blue> Jeff - may the force be with you</font color=blue>
     
  3. Thunder

    Thunder 3/4 ton status

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    Well I asked my wife and some of her firends who are over. They all agreed, " Yes size does matter" They also said that 2 1/4" dia would be just fine.
     
  4. Twiz

    Twiz 1/2 ton status

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    From what Jeff said, I would do the K And N filter AFTER the exhaust mods, so you can feel what you what you paid for with the K and N filter.

    As far as pipe dia.. The idea is to keep the exhaust flowing out of the pipe, and not to have atmisphirice (S/P?) pressure pushing back. So, in a nut shell, vilosity (S/P?- sorry it's late) is the key word. Reduseing back pressure will allways improve performance AND fuel economy! As long as the air/fuel and timeing is adj as needed to match. But, keep in mind, too large of a pipe- will allow air-pressure to work against the exhaust pulse.

    In short;
    2 1/4" pipe with a well designed full length exhaust sys. should produce the the best "all-around" perfomance packege. Clean welds, smooth reductions in pipe, smooth flowing bends, etc., nothing abrupt.
    I think, a clean designed exhaust sys with even 2" pipe, could flow enuff for a small-blocked engine w/a idle to 4500 RPM opperating range. But, we should/have to deal with the t-case cross member and rear wheel well hump, so, the diameater would have to be enlarged to compensate for it.

    Twiztid
    This is all about opinions, and this is mine. (if applicible)
     
  5. 84_Chevy_K10

    84_Chevy_K10 Banned

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    The deal here is the same with everything else. EVERYTHING MUST MATCH. That means you must have the right size intake, camshaft, headers, and exhaust.

    I have a 500 CFM carb, Performer intake, a mild Comp Xtreme 4x4 cam, 1 1/2" headers and 2 1/4" pipe on my 305. Believe it or not that's good for 250 HP and 330 ft-lbs. of torque, the same as a Goodwrench 350 crate motor.

    The deal is with component selection, everything must match. If anything doesn't, it won't work well.

    If my motor was a 350 but otherwise the same, I'd probably use 2 1/2" pipe.

    The theory, "smaller for more torque, bigger for more HP" only works to a point. You can use pipe size to tune your engine in somewhat, but everything working together will produce the best response.

    Unfortunately, dual 2 1/2" pipe sounds better. Dual 3" sounds even better than that. I have 2 1/4 though because I have a small engine and have to maximize performance. If I could have whatever I wanted, I'd have 3" duals just for sound and I wouldn't even care. But I know that performance is more important, so I've got 2 1/4.

    I've got the Dynomax kit. Took and hour to install and I could buy two or three of them for what a muffler shop charges. Worth every penny and very easy to install.

    Tim
    '84 Chevy K10, lifted, loud, fast, and 3/4 ton axles
     
  6. husurddy

    husurddy 1/2 ton status

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    Great info so far. I guess I'll go 2 1/4, but do I need the H pipe between the duals? I have read several posts some say yes others dont mention it. What are the advantages/ disadvantages?
     
  7. Emmettology 101

    Emmettology 101 3/4 ton status

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    BuuuuuHHHaaaaaaaaaaaa!!!!!!!!!!!!!!!!!!!!!!!! [​IMG]

    Mike

    <font color=green>"It's like a sore dick deal, You cant beat it!"</font color=green>

    <a target="_blank" href=http://www.geocities.com/emmettology101>www.geocities.com/emmettology101</a>
     
  8. Emmettology 101

    Emmettology 101 3/4 ton status

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    BuuuuuHHHaaaaaaaaaaaa!!!!!!!!!!!!!!!!!!!!!!!! [​IMG]

    But what happened to: "It's not the size of your wand, it's the magic in it!" ???

    LOL

    Mike

    <font color=green>"It's like a sore dick deal, You cant beat it!"</font color=green>

    <a target="_blank" href=http://www.geocities.com/emmettology101>www.geocities.com/emmettology101</a>
     
  9. white_knight

    white_knight 1/2 ton status

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    I put a 3" exhaust when I had my 305. It worked great. I kept it 3" with the 454. Sounds nasty.

    <a target="_blank" href=http://www.whiteknight.scriptmania.com/>http://www.whiteknight.scriptma
    nia.com
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  10. white_knight

    white_knight 1/2 ton status

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    I put a 3" exhaust when I had my 305. It worked great. I kept it 3" with the 454. Sounds nasty.

    And yeah, size does count :)

    <a target="_blank" href=http://www.whiteknight.scriptmania.com/>http://www.whiteknight.scriptma
    nia.com
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