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  1. #1
    Jr. Apprentice
    Join Date
    Nov 2009
    Location
    Vancouver, WA
    Posts
    26

    Default What's your exhaust opinion

    1977 Chevy 1/2ton 4x4 SWB with small block 400 with stock 4bbl Qjet and stock intake (I will be staying with the Qjet but replacing the intake soon. )

    Ok, so the existing collectors are crap, got holes sounds like junk. Currently i have true dual 2 1/2" pipes running half the length of the truck to cherry bombs. They sound ok, but with the leaks up front, it's killing me. I am sure i'm losing a ton of pressure up front when i accelerate.

    Stopped by a local shop today and talked with the owner, nice guy, and he suggested dual 2 1/4" Flowmaster headers to dual 40 series flowmaster mufflers out to stock side exits. Which is what I am thinking I want it to look like. He will do it all for $450.

    Question is: Am i going to be losing too much backpressure running true dual? should i go 2 into 1 with 3" pipe out?
    1977 Chevy K10 SWB 4x4 all stock 400SB
    "Work in Progress"

  2. #2

    Default

    That sounds like a good setup.
    Two things I'd do different would be a crossover between the headers and mufflers and 2" pipe.
    You arent running cat convertors on this truck?

  3. #3
    Jr. Apprentice
    Join Date
    Nov 2009
    Location
    Vancouver, WA
    Posts
    26

    Default

    No, no Cat, the beauty of being old!Are you talking a crossover as an equalizer? i had one on my Harley Sportster a long time ago...

  4. #4
    Master Mechanic TritonBoulder47's Avatar
    Join Date
    Nov 2009
    Location
    Tunkhannock, PA (North East)
    Posts
    809

    Default

    True duals are the way to go, but throw an X-pipe in there... Just to equalize back presure...

    Tim a.k.a. Da' Boulder

    2003 Chevrolet Avalanche Z71 - Custom Emergency Response POV

    Firefighter, Fire Policeman, Ambulance Driver, Rescue Tech, Emergency Lighting Installer

    Tint, 20's, Bull Bar, Intake, Exhaust, Billet Grill, Stereo, Custom Console, Emergency Equipment, and the list goes on...

  5. #5

    Default

    1977 was the first year for mandatory catalytic convertors on all vehicles under 3/4ton sold in the U.S. Auto manufacturers stopped using smog pumps and nox systems due to the "new" (at the time) requirement of catalytic convertors. If this is a 1977 truck it came from the factory with a catalytic convertor. Manufactures also stopped putting dual exhaust on vehicles at that time due to the expensive cost of a second convertor.
    Not sure how Washington state emissions regulations are but most states that have inspection laws covering vehicles this old will make you put catalytic convertors back on.
    Most muffler shops wont take catalytic convertors off because they face large fines and possible legal action but if the vehicle doesnt have them and the shop is unsure if the vehicle came factory with them wont sqwauk about putting them on when you replace the exhaust.
    Yea a crossover is the same thing as an equalizer and does the same thing as an "X" pipe.

  6. #6
    Jr. Apprentice
    Join Date
    Nov 2009
    Location
    Vancouver, WA
    Posts
    26

    Default

    The truck is exempt from emissions in Washington because is is over 25 years old, so I don't actually have to go through testing anymore, so I am good there.

    I was talking to a friend who had mentioned going with 3"duals but I am thinking that I will be losing to much back pressure that way. Any thoughts?

  7. #7

    Default

    Where do you drive the truck most?
    If its in town most I'd stick with 2" to 21/2"
    If its on the highway mostly3" might work better.

  8. #8

    Default

    I've had my truck for so long, I remember laying on the gravel, in the rain, hacking my catalytic converter off with a hack-saw back in the 80's. Late 80's. If I'm not mistaken, I tossed it in an unused corner of the garden, and let it return to nature.

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