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Help!! please??

Discussion in 'The Garage' started by Confedneck79K30, Jan 27, 2007.

  1. Confedneck79K30

    Confedneck79K30 3/4 ton status

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    so i put in the new procomp billet hei dist and new msd wires, installed the rad and temporarily mounted the electric fans.... it still wont idle very well...

    350 with a qjet (supposedly new reman)

    when i start it up, it idles high, and backfires or pops out of the exhaust (has rotted out true duals with only one muffler).... when i try to accelerate it just bogs... but if i feather the throttle it will rev up almost in stages...


    it will idle for about 30-45 seconds and then slowly die out....


    i turned the adjustment screws all the way in, then out 1.5 turns and it backfired through the carb so i figgered before i blew the pos up, id better ask for help...

    what can i do to make this thing idle? all thats left is to make it run decent, actually wire and mount the fans, install the hood and brake booster and we're good to go...
     
  2. ryoken

    ryoken Puppy Fabricator Premium Member GMOTM Winner

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    Well, it could certainly be a valve issue.. It could be your dizzy improperly set up too... A lean issue can also pop out the carb, but I'm betting it's in the valvetrain or timing of their operation...

    First thing I'd do is walk onto your truck, get a compression tester and start with the basics.. You'll know quick if you've got a valve hanging up...

    How did you set up the dizzy? 100% sure the firing order is right?
     
  3. Confedneck79K30

    Confedneck79K30 3/4 ton status

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    yeah, it ran the exact same before i swapped dizzy... ive been told i have a burnt valve, but will that make it not idle at all?

    i put the new dist in exactly where the old one was, not saying that was correct thought...
     
  4. ryoken

    ryoken Puppy Fabricator Premium Member GMOTM Winner

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    Do a compression or leakdown test... simple to do and you'll know right away about the valves...
     
  5. Confedneck79K30

    Confedneck79K30 3/4 ton status

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    i was a mechanic, but never did any heavy line (engine) work... so a compression test will tell me if the engine is making good compression, but what will it tell me about the valves?
     
  6. readymix

    readymix 3/4 ton status

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    Leakdown will tell you more than the compression ever will.
     
  7. ryoken

    ryoken Puppy Fabricator Premium Member GMOTM Winner

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    Well, it's pretty simple. if you have cylinder that fails compression, add a couple tablespoons of oil to it and do it again.. if compressions comes up, it's a ring issue.. stays the same, it's an intake or exhaust.. You wont know which, but it really doesn't matter, the head'll have to come off...

    a leakdown will tell you if it's a intake, exhaust or rings right off the bat..
     
  8. Confedneck79K30

    Confedneck79K30 3/4 ton status

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    ok so if the truck has a valve issue, is there anything ( i doubt it) temporary i can do to keep it running?i have a code violation issue with this pos and they want it running monday...
     
  9. 4xcrazy

    4xcrazy 3/4 ton status

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    I was having some similar issues with this 81 i have here with the 350, went through several (used) Quadracrap carbs, couldn't get any of them to work right. I even rebuilt two different carbs, still didn't want to run right, so i just swapped out the intake and threw on a Edlebrock and now it runs awsome.

    Personally i think it's a game of chance with a rebuilt quadrajet, for me either brand new, or nothing.

    Double check your timing, you said it backfired out the carb, good sign, then if you can try a different carb, maybe borrow one or something to get an idea.
     
  10. Confedneck79K30

    Confedneck79K30 3/4 ton status

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    ok so i checked compression
    front to rear
    drivers side
    140
    140
    125
    140

    pass side
    140
    125
    125
    140


    watcha think? it sounds like its backfiring, when it does it through the carb, it is when its starting, and at idle out the exhaust...

    it did this with the old acdelco dist and holley...
     
  11. Confedneck79K30

    Confedneck79K30 3/4 ton status

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    could it be that the battery is almost dead and it needs a jump box to start it? low voltage issue?

    also, where should the vac line for the advance be hooked to?i moved it from the lowest drivers side port, to the highest pass side port with no change... also put new plugs on the rest of the vac ports...
     
  12. ryoken

    ryoken Puppy Fabricator Premium Member GMOTM Winner

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    Not if your alternator is putting out..... It wont be a low voltage issue... If it lights, it should run...

    Those comp #'s are questionably ok, but it should run... the normal % you want to see is no more than 10% difference between cylinders on a gas V-8. Those 125's are a tad more than that... But it shouldn't effect it running..

    vac advance shouldn't matter much, some peeps prefer non-ported, some ported.. anything below the throttle plate is non-ported, thats usually where I run them....

    What's your base timing set to?
     
  13. Confedneck79K30

    Confedneck79K30 3/4 ton status

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    no timing light, ,how do i tell?
     
  14. Confedneck79K30

    Confedneck79K30 3/4 ton status

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    ive tried adjusting the timing before to no avail, as well... but would timing cause it to run then bog down and die? maybe loading up?
     
  15. ryoken

    ryoken Puppy Fabricator Premium Member GMOTM Winner

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    You can't....

    How does it crank? Are you sure the voltage is low and it's not the timing being off?
     
  16. Confedneck79K30

    Confedneck79K30 3/4 ton status

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    well the battery was flat dead, i hooked the jump box to it and it cranks, a little slow still, though
     
  17. gmc4cw

    gmc4cw 1/2 ton status GMOTM Winner

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    go get a timing light. trying to set it without the light is futile. sounds to me that your timing is much further off then you would think.

    1-8-4-3-6-5-7-2
     
  18. Confedneck79K30

    Confedneck79K30 3/4 ton status

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    so i can double check, where is cyl.1 in the dist?
     
  19. 4xcrazy

    4xcrazy 3/4 ton status

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    uuuuh, wherever your #1 sparkplug wire is going to???:confused:
     
  20. ryoken

    ryoken Puppy Fabricator Premium Member GMOTM Winner

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    You shouldn't be looking at "where is cyl 1 on the dizzy" It reallly doesn't matter.. as long as you start lacing the wires from the point the rotor is facing when the dizzy is TDC..

    Just hook the pickup on the wire down by the cylinder to check timing.. #1 is driverside all the way forward.... make sure you disconnect and plug the vac advance line..

    I'm betting somethings wrong with this ignition with the fact it's popping out exhaust and carb...
     

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