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Straight pipes on a 1979 K5 400SB

Discussion in 'The Garage' started by BozoWise, Jul 5, 2002.

  1. BozoWise

    BozoWise 1/2 ton status

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    Is it bad on the motor to run straights. I am only running my K5 as a trail and mod-bog rig and hate the way that it sounds. I am about to have to remove the crossover pipe and was wondering if it would hurt to drive it without mufflers while I was working on the exhaust. I have some undercarriage things to work out and it will be a few months before I get the compete exhaust done with flowmasters.
     
  2. bigmack

    bigmack 1/2 ton status

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    It hasn't hurt anyhting on my truck. I have 3" dual pipes with no mufflers. It has been that way for 5-6 months and counting.
     
  3. 1979Jimmy

    1979Jimmy 1/2 ton status

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    I dont think it will hurt anything as long as you run them all the way out the back. If you run them just out of the headers or manifold your feet will be real hot and so will your tranny.

    Youll also loose low rpm power but if your running mud you probably dont care.
     
  4. BozoWise

    BozoWise 1/2 ton status

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    Has anyone tried putting turn downs dropped right before the rear axel? Does it gas you in the cab with the rear window down?
     
  5. thatK30guy

    thatK30guy 1 ton status Premium Member

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    I had an F150 years ago that I ran straight pipes on. They went all the way back behind the rear tires. Only got loud when I got on it. /forums/images/icons/laugh.gif

    I have heard that open headers or even a short length of pipe is not good on the valves as they can get hot and warped. Not sure if this is true or not.
     
  6. 1979Jimmy

    1979Jimmy 1/2 ton status

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    Ive heard that but i was under the impresion that that was really only with very short pipes.
     
  7. backyardbuilt

    backyardbuilt 1/2 ton status

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    Some drag race guys told me to put a 3 1/2 foot section of pipe on after the header and mark it with a white crayon and run the vehicle up to operating temp and where the crayon didn't melt all the way off cut your pipe there and you'll be fine.
     
  8. thatK30guy

    thatK30guy 1 ton status Premium Member

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    But be aware that some drag race engines use different valves than regular street engines do.

    Some of those valves are the 'severe duty', etc. mainly for this type of driving...race.

    I would still put on a longer pipe than how you explained to do it since the engine needs to have some back pressure in order to have its proper performance.

    I had an '86 K10 with a 350 and headers once. I ran the truck open headers to move it around the garage and noticed that when I drove it like this, there was no power at all. All that exhaust just blew right out of the headers. I thought there was something else wrong.

    Then I got the exhaust installed and drove it again. The truck had power finally. It ran much better than it did open headered. The new exhaust had given the engine some back pressure and allowed it to run like it should. /forums/images/icons/wink.gif
     
  9. BozoWise

    BozoWise 1/2 ton status

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    Anyone have any info on dumping the pipes infront of the rear axel and if it'll gas me ;-)
     
  10. thatK30guy

    thatK30guy 1 ton status Premium Member

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    I've wondered that, too.

    My '84 Blazer that I sold a few months ago had a broken/missing tailpipe assembly and it ALWAYS leaked the fumes into the cab no matter how fast or where I drove. /forums/images/icons/tongue.gif

    The passenger side pipe/muffler totally fell off right at the t-case. The fumes leaked into the cab from there.

    Guess I had too much rust holes all over the bottom of the body. /forums/images/icons/blush.gif /forums/images/icons/laugh.gif /forums/images/icons/grin.gif
     
  11. BozoWise

    BozoWise 1/2 ton status

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    I know someone out there has or has tried to dump the pipes at the rear axel. Did you get fumed?
     
  12. bigmack

    bigmack 1/2 ton status

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    Like I stated before, I have 3" duals with no mufflers, my pipes have a turn down right at the rear axle. It is not a problem with the gas fumes at all, even sitting still. My truck is a K10, I don't know if it would be different with a K5.
     
  13. 1979Jimmy

    1979Jimmy 1/2 ton status

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    I assume you have to have your vehical inspected seeing as it is a 79 I cant tell you if you would get gassed or not but it would be illegal because in passenger cars the pipes must extend past the passenger area. Since the bed in a k5 is enclosed and technically part of the passenger area the exhaust must exit being the tailgate. At east that is what I have been told. Somebody wil correct me if i am wrong.
     
  14. NITRO

    NITRO 1/2 ton status

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    Speaking of, thats exactly what im gonna do in the next few weeks. Im gonna do turn downs right bfore the axle. but, i think i will put on small flowmasters to cause some backpressure. otherwise, it will mess up ur valves and u'll lose HP. unless ur truck is set up for this.ill let ya all know

    NITRO
     
  15. have this set up now on my 76 long box. dumps right before the rear axle. no fumes in the cab. used to have a 77 short wide that dumped right after the cab. just had headers into glass packs and then out. no fumes.

    oddly though, in the blue beast (oh how i miss her) i had pipes that exited out the sides behind the rear tires. when i did my shackle flip i cut them just enough to clear the springs- pipes still pointed out but were under the bed. got fumes. go figure.
     
  16. BorregoK5

    BorregoK5 1/2 ton status

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    I have yet to route my exhaust anywhere on the truck (and I've tried) and not get fumed one way or another with the top on! /forums/images/icons/mad.gif
     
  17. 1979Jimmy

    1979Jimmy 1/2 ton status

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    If you do a search i looked up htis exact same question like 6 months ago.
     
  18. BozoWise

    BozoWise 1/2 ton status

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    In the great state of NM we have no inspections /forums/images/icons/smirk.gif
     
  19. Leadfoot

    Leadfoot 1/2 ton status Premium Member

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    </font><blockquote><font class="small">In reply to:</font><hr />
    In the great state of NM we have no inspections

    [/ QUOTE ]

    I know where I'm moving......Lucky Ba*^*&amp;^ /forums/images/icons/laugh.gif
     
  20. BozoWise

    BozoWise 1/2 ton status

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    Most of the land is state owned so you can hunt just about anywhere also /forums/images/icons/cool.gif
     

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