Dismiss Notice

Welcome To CK5!

Registering is free and easy! Hope to see you on the forums soon.

Score a FREE t-shirt and membership sticker when you sign up for a Premium Membership and choose the recurring plan.

torquie exhaust

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

  1. aaaaggh

    aaaaggh 1/2 ton status

    Joined:
    May 4, 2001
    Posts:
    161
    Likes Received:
    0
    Location:
    birmingham alabama cause there no ham like birming
    ok im ready to drop in my engine but im not sure what do do about exhaust. the engine is making about 330 hp and just over 400 ft lb. that of course is only at the block. what kind of exhaust does everyone like for high torque. i want it to sound ok but torque is much more impoortant than sound. ill have to use stock manifolds for my application since headers that will fit will be way too expensive.

    friends romans countrymen, lend me some parts
     
  2. Emmettology 101

    Emmettology 101 3/4 ton status

    Joined:
    May 9, 2000
    Posts:
    8,126
    Likes Received:
    0
    Location:
    FL
    2.5" duals with Flows and a x-over pipe??

    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>
     
  3. Rockjunkies

    Rockjunkies 1/2 ton status

    Joined:
    Jul 26, 2001
    Posts:
    385
    Likes Received:
    0
    Location:
    Oklahoma
    A single 2-2.5 in pipe will generally create more torque than 2.5 duals. I am not to sure why that is, I would have to study up on it again. But I think it has something to do with back pressure. 2.5 duals is good for a high rpm motor, but it will hurt the low end torque. If you insist on having duals, keep the diameter of the pipe to a min. and use the cross over pipe.

    Keep it simple!
     
  4. solowookie

    solowookie 1/2 ton status

    Joined:
    Mar 31, 2001
    Posts:
    3,880
    Likes Received:
    0
    Location:
    Wyoming
    <blockquote><font class="small">In reply to:</font><hr>

    A single 2-2.5 in pipe will generally create more torque than 2.5 duals. I am not to sure why that is, I would have to study up on it again. But I think it has something to do with back pressure. 2.5 duals is good for a high rpm motor, but it will hurt the low end torque. If you insist on having duals, keep the diameter of the pipe to a min. and use the cross over pipe.

    <hr></blockquote>

    yea, but I think this also depends on how much HP your running etc. I'm sure there are others that can explain that. (and maybe I'm crazy too [​IMG])

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

    pcorssmit 1/2 ton status

    Joined:
    Jan 2, 2001
    Posts:
    1,346
    Likes Received:
    0
    Location:
    Denver, CO
    I'd go 3" single. I think the single helps the scavenging at low rpm.

    Pete

    '83 K5, 350 TBI (ex 6.2), 700R4, NP208, Dana 60/14 bolt, 4.56s, Detroits, 3" lift, 15-39.5x15 TSLs
    '97 Dodge 2500 4x4 CC LB Sport, Cummins 5 spd
     
  6. 84_Chevy_K10

    84_Chevy_K10 Banned

    Joined:
    May 30, 2001
    Posts:
    17,669
    Likes Received:
    0
    Location:
    IL, USA
    Go with the 2.5" duals with crossover. That motor needs to breathe. Get headers too (1 1/2" primary, for torque).

    If you insist on small pipe, you can get 2 1/4. I've got a 250/330 hp/tq. motor and I use 2 1/4". DD2000 says my torque peak is 3000 RPM.

    If you insist on a single exhaust, a 3" will probably be enough. I'd still rather have the duals, with crossover.

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

    CaptCrunch 1/2 ton status

    Joined:
    Feb 2, 2001
    Posts:
    3,596
    Likes Received:
    1
    Location:
    Minnesota
    I personally recomend 2 1/4" exhaust w/ a crosover or X pipe for max torque... also would recomeend it being off Thorley headers. Backpressure is a big part of having torque...gotta have th right amount... not too much... not too little

    -Mikey
    1987 Chevy K5 Blazer- 350 TBI
    <a target="_blank" href=http://www.geocities.com/milnerlives_2000/blazer.htm>http://www.geocities.com/milnerlives_2000/blazer.htm</a>
     
  8. Twiz

    Twiz 1/2 ton status

    Joined:
    Mar 8, 2001
    Posts:
    3,729
    Likes Received:
    0
    Location:
    Clearfield Ut.
    Doesn't much matter with the stock manifolds, since the stock manifolds will be the restriction in the sys.

    Twiztid
    This is all about opinions, and this is mine. (if applicible)
     
  9. pcorssmit

    pcorssmit 1/2 ton status

    Joined:
    Jan 2, 2001
    Posts:
    1,346
    Likes Received:
    0
    Location:
    Denver, CO
    "I'd still rather have the duals, with crossover."

    Why?

    Pete

    '83 K5, 350 TBI (ex 6.2), 700R4, NP208, Dana 60/14 bolt, 4.56s, Detroits, 3" lift, 15-39.5x15 TSLs
    '97 Dodge 2500 4x4 CC LB Sport, Cummins 5 spd
     
  10. 84_Chevy_K10

    84_Chevy_K10 Banned

    Joined:
    May 30, 2001
    Posts:
    17,669
    Likes Received:
    0
    Location:
    IL, USA
    The tuned part of your exhaust system doesn't go very far anyway. After about the first 50" I'm told the more restriction you can reduce, the better. However, if you run too big of pipe, it will cool too much, lose velocity, and then you'll start loosing power.

    I'd rather have the true duals becuase they sound FAR better and will still allow good scavenging--and reduce backpressure.

    The headers/manifolds and some of the pipe produce all the backpressure you could possibly want. After that's just restriction. Obviously you've got to get the fumes away from the passenger compartment, so you should really run a full exhaust on a K5.

    I wouldn't put single exhaust on anything around here. We don't have emissions so we have our choice.

    Dynomax makes a great kit for dual exhaust. I have the header duals. http://mavericktim.freeyellow.com/exhaust.jpg&gt; Here is a picture so you can see how it routes. It has side exit pipes behind the rear wheels and is quite cheap compared to muffler shops. I know, I don't have a crossover yet. I'm working on that, I just haven't got around to ordering that kit yet. I want one.

    Edit:
    I have a K10 shortbox, not a K5. For a K5, you just remove the extension pipes that go directly behind the mufflers on mine and run the tailpipe straight to the muffer and it'd fit perfectly. It took me about 60 minutes to install the pipes after the headers were done.

    Tim
    '84 Chevy K10, lifted, loud, fast, and 3/4 ton axles&lt;P ID="edit"&gt;&lt;FONT class="small"&gt;&lt;EM&gt;Edited by 84_Chevy_K10 on 08/10/01 01:17 AM.&lt;/EM&gt;&lt;/FONT&gt;&lt;/P&gt;
     
  11. pcorssmit

    pcorssmit 1/2 ton status

    Joined:
    Jan 2, 2001
    Posts:
    1,346
    Likes Received:
    0
    Location:
    Denver, CO
    "The headers/manifolds and some of the pipe produce all the backpressure you could possibly want. After that's just restriction."

    So, if I run manifolds with a couple feet of straight pipe, say dumping under my feet, I should get lots of torque?

    "Obviously you've got to get the fumes away from the passenger compartment, so you should really run a full exhaust on a K5."

    Agreed.

    "I wouldn't put single exhaust on anything around here. We don't have emissions so we have our choice."

    I have my choice as well, I have a waiver from the state saying I can legally run duals on my truck. I choose not too.

    Pete

    '83 K5, 350 TBI (ex 6.2), 700R4, NP208, Dana 60/14 bolt, 4.56s, Detroits, 3" lift, 15-39.5x15 TSLs
    '97 Dodge 2500 4x4 CC LB Sport, Cummins 5 spd
     
  12. Mreetz

    Mreetz 1/2 ton status

    Joined:
    Jun 26, 2001
    Posts:
    1,282
    Likes Received:
    0
    Location:
    Subs of Denver, Colorado
    I saw an add for a dual exhaust you could mail order, they were 150.00. Anyone remember seeing this or what company it was?
    thx

    1984 K-5
    4" lift
    35x12.5 MTs
    buildin a 400 for it, any info greatly appreciated
     
  13. WOODYJ

    WOODYJ 1/2 ton status

    Joined:
    May 5, 2000
    Posts:
    144
    Likes Received:
    0
    I am running the Thorley stainless torque headers and then just a run of the mill dual system. I will say this for the Thorley headers--they produce torque!!! I do have problems with them burning my spark plug wires now and then. Also it is almost impossible to change spark plugs!! If I had it to do over, I would not use the Thorley headers and stick with the stock manifolds. Much easier to work on, saves thousands of "Truck Driver Words", and doesn't take so much spark plug wire.

    k5woody I Don't Understand The Jeep Thing Either!!!
     
  14. Blazer79

    Blazer79 1/2 ton status

    Joined:
    Feb 17, 2000
    Posts:
    1,816
    Likes Received:
    0
    Location:
    Guatemala, Central America
    If you can't afford the Thorley's, you could get a set of Flowtech Afterburners. That's what I'm using now and my torque did come up. I can't say it was a lot, but I currently only have the stock 350 engine.

    I think that if your engine has an appropriate cam, you won't lose that much torque with a large exhaust. A slightly restricted exhaust prevents the fresh fuel charge from escaping during valve overlap, but unless you have a radical one, the cam prevents that by allowing less exhaust time. Too much restriction will hurt anyway since it takes more power to move the gases out. It's your choice anyway, so pick one of the following exhaust areas:

    Single 2.25" = 3.53 sq. In. (I think this is what came stock)
    Single 2.5" = 4.91 sq. in.
    Single 3" = 7.07 sq. in.
    Dual 2.25" = 7.06 sq. in.
    Dual 2.5" = 9.82 sq. in.
    Dual 3" = 14.14 sq. in.

    I currently have Dual 2.5" with an H-pipe and a pair of Flowmasters. It sounds nice. Although I'm not sure, it will have to work with the 454 since I have no $$$ for replacing the system right now.

    Good luck and let us know what you decide.

    <font color=purple>//////
    <a target="_blank" href=http://blazer79.freeyellow.com>blazer79.freeyellow.com</a></font color=purple><font color=black>
    Soon a 454 K5!!</font color=black>
    [​IMG]
     
  15. 84_Chevy_K10

    84_Chevy_K10 Banned

    Joined:
    May 30, 2001
    Posts:
    17,669
    Likes Received:
    0
    Location:
    IL, USA
    I can't believe you CAN run dual exhaust, yet you don't. To me that's silly. I guess it must have been cheaper to run a single.

    &gt;&gt;&gt;So, if I run manifolds with a couple feet of straight pipe, say dumping under my feet, I should get lots of torque? &lt;&lt;&lt;

    Absolutely, if you use the correct size headers and pipe to match your engine. If everything is matched correctly, it works best, period. Theoretically the best exhaust system is one with the least restriction. So, the right size system that was extrememly short would be best.

    I don't like how you said, "I should get lots of torque". That depends on an awful lot of things. Exhaust systems aren't going to make a major change in the torque curve of your motor. You can either use an exhaust to take advantage of what your motor has to offer, (hopefully exhaust is set up for peak torque RPM of the motor to be at about the same that the exhaust is tuned for) or you can choke it until it makes drastically less power, but usually any aftermarket or custom exhaust will fall somewhere between those two extremes.

    I've made many exhaust systems. I know that mine works very well with my setup, and although I'd love to have bigger pipe for sound purposes, I am keeping my 2 1/4" pipe for torque, so it can match the carb, intake, cam, heads, and header primary tube size.

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

Share This Page