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.

3" exaust?

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by BillyBob, Oct 3, 2001.

  1. BillyBob

    BillyBob 1/2 ton status

    Joined:
    Feb 23, 2000
    Posts:
    557
    Likes Received:
    1
    Location:
    Dumont, NJ
    3\" exaust?

    Well, plans for a 3" single exaust for my truck are forming. So far I got a 3" flowmaster for $45, and plan on getting a 3" cat from summit. I may also swap the EFi from my 87 over. Now, will the larger exaust screw up my EFI because it's flowing a lot better? I've heard of some EFI systems running a little rich due to larger exausts. Dunno if it's true, but it's what I've heard. I just hope this custom cat back will give me more power. Right now the truck is slow as crap, and I don't think it's the gearing. Geeze I need to ditch this target replacement for a ZZ crate motor...

    <a target="_blank" href=http://billybob87k5.50megs.com>Homepage of Porky & Stinky</a>
    ".. Sanatarium.. leave me be..."
     
  2. riz

    riz 3/4 ton status

    Joined:
    Mar 7, 2000
    Posts:
    6,026
    Likes Received:
    0
    Location:
    Wisconsin
    Re: 3\" exaust?

    <font color=purple> I was always under the impression that you need to have a good amount of motor to run bigger exhaust ? Am I right or just tired ?

    L8r,
    . Riz . <a target="_blank" href=http://www.geocities.com/rizmonkey>www.geocities.com/rizmonkey</a>

    <font color=purple> BOW CHICKA BOW WOW !
     
  3. solowookie

    solowookie 1/2 ton status

    Joined:
    Mar 31, 2001
    Posts:
    3,880
    Likes Received:
    0
    Location:
    Wyoming
    Re: 3\" exaust?

    I've got 2 k5's with TBI... one with true dual 2 1/2" exhaust pipes with no cats, and a 3" gibson catback with no cat. on it. in both cases the vehicle only ran better, and it didn't run rich or anything else like that.

    <font color=blue> Jeff - may the force be with you</font color=blue>
    <a target="_blank" href=http://coloradok5.com/gallery/Jeffs-Stuff>link to k5's</a>
     
  4. solowookie

    solowookie 1/2 ton status

    Joined:
    Mar 31, 2001
    Posts:
    3,880
    Likes Received:
    0
    Location:
    Wyoming
    Re: 3\" exaust?

    from everything I've studied / gotten replies on a 3" single exhaust isn't a problem.

    <font color=blue> Jeff - may the force be with you</font color=blue>
    <a target="_blank" href=http://coloradok5.com/gallery/Jeffs-Stuff>link to k5's</a>
     
  5. xnoahx

    xnoahx 1/2 ton status

    Joined:
    Oct 12, 2000
    Posts:
    817
    Likes Received:
    0
    Location:
    Ventura, CA 93004
    Re: 3\" exaust?

    3" single is fine for a small block, 3" duals for a small bolock is not too good for torque

    My 73 K5 <a target="_blank" href=http://www.geocities.com/xk5blazerx/73k5.htm>http://www.geocities.com/xk5blazerx/73k5.htm</a> 350/TH350/NP203, Q-jet, Edelbrock intake, Vortec heads, 4" lift, and 36" TSL's
     
  6. Cmoe

    Cmoe 1/2 ton status

    Joined:
    Feb 19, 2000
    Posts:
    2,884
    Likes Received:
    0
    Location:
    Mesa,AZ
    Re: 3\" exaust?

    I was looking at eather going with a 3" or dual 2.5" and saw a guy here in AZ that had a 3" and it hung down low.... Eveeryone is surprised that I have a true dual on my K-5 due to the Rig looks like an '87

    C'moe

    Kill Roy was here!
     
  7. Thunder

    Thunder 3/4 ton status

    Joined:
    Jul 20, 2000
    Posts:
    8,946
    Likes Received:
    1
    Location:
    Northeast Nevada
    Re: 3\" exaust?

    I have a 89 TBI 350. I'm running 3" single exhaust with a 70 series flowmaster. This set up works great. It builds a good ammount of torque and helped get better gas milage too. It was a major improvement over the stock system.

    <a target="_blank" href=http://coloradok5.com/gallery/Thunders-Blaze>http://coloradok5.com/gallery/Thunders-Blaze</a>
    <font color=blue>NEVADA: Where the pavement ends, and the West begins.</font color=blue>
     
  8. blazer72

    blazer72 1/2 ton status

    Joined:
    Apr 13, 2000
    Posts:
    939
    Likes Received:
    0
    Location:
    KCMO
    Re: 3

    The 87 and up stock y-pipe is 2 3/8 or 2 1//2 to one 3 inch singel pipe so I dont think you will mess up much with the TBI. My 72 runs a 87 y-pipe to a 87 truck 7.4 muffler. Lots of low end but my ears dont ring after a day of 4 wheeling

    72 Blazer CST 400TPI NV4500 NP203/205
    01 Suburban 2500 4X4 8100
     
  9. solowookie

    solowookie 1/2 ton status

    Joined:
    Mar 31, 2001
    Posts:
    3,880
    Likes Received:
    0
    Location:
    Wyoming
    Re: 3\" exaust?

    you might even wanna go down to 2 1/4 for a 350...I went 2 1/2 on insane ewok, and now I wish I would have went 2 1/4.

    <font color=blue> Jeff - may the force be with you</font color=blue>
    <a target="_blank" href=http://coloradok5.com/gallery/Jeffs-Stuff>link to k5's</a>
     
  10. BowtieBlazer

    BowtieBlazer 1/2 ton status

    Joined:
    Jul 15, 2001
    Posts:
    2,462
    Likes Received:
    0
    Location:
    Baton Rouge, Louisiana
    Re: 3

    Here is how you do it seriously! The stock exhaust is 2 ½" in some places and 3" in others. If you want to get the biggest improvement, do the cat first. Have the muffler place cut the stock pipe just before the reducer to 2 ½" and insert that new cat. If they have to, cut the exhaust back to where the two pipes join from the heads. It is 3" at that point. Also, run 3" pipe into the muffler from the cat. This was the biggest improvement that I noticed, both in mpg and torque.

    What? You think the hole is too deep? Lemme see...
    1985 GMC C-10 Shortbed
    1984 Chevy K-5 Blazer
     
  11. Itali83

    Itali83 1/2 ton status

    Joined:
    Feb 12, 2001
    Posts:
    795
    Likes Received:
    0
    Location:
    Westbrook Maine
    Re: 3

    I have an 87 TBI. I bought a high flow honeycomb style 3" cat. then I got a 3" flowmaster force 2 system, all 3" mandrel bent with 50 series. This system ROCKS. My truck is totally different now, it has much more pickup, much better gas mileage. DO 3" !!!!!!!!
    Ben 87 Jimmy
    <font color=blue>Rust=Bad</font color=blue>
    <a target="_blank" href=http://www.bens87toy.alloffroad.com>www.bens87toy.alloffroad.com</a>
     
  12. Jersey

    Jersey 1/2 ton status

    Joined:
    Aug 14, 2001
    Posts:
    234
    Likes Received:
    0
    Location:
    NJ
    Re: 3

    i'm using 3" all the way back with the highflow and 50series from flowmaster w/efi and she runs great. nice improvement all the way around.

    '91K5 - 350, 700R4, NP241, Flowmaster
    <a target="_blank" href=http://pages.zdnet.com/len1313/blazer>[/b]PICS[/b]</a>
     
  13. 84_Chevy_K10

    84_Chevy_K10 Banned

    Joined:
    May 30, 2001
    Posts:
    17,669
    Likes Received:
    0
    Location:
    IL, USA
    Re: 3

    I have 2 1/4" true duals. 2 1/2" pipe sounds better but isn't as good for torque.

    I suggest you go with 3" tubing if you have to run single, 2 1/4" if you can run duals.

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

Share This Page