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I want to put a fuse in my gas tank and Get rid of this headache PLS heLP!!

Discussion in 'The Garage' started by Silver84k5, Aug 5, 2002.

  1. Silver84k5

    Silver84k5 1/2 ton status

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    ok ive gone this far so i know i cant turn back cuz i will lose all sorts of money and ill never get to test my work but.... I cant get my engine to stop backfiring through the Carb, Ive put on a edelbrock 850 q jet, Ive put on a stock replacement rochester q jet, ive put on MSD 6a box, MSD coil inside the Cap, New MSD wires, New plugs, Try Timing at 5 8 10 and 12, it has a Medicore cam, maybe a little more then mediocre, What else would it be? when we put the msd in i kept trying different carbs, then my plugs got fowl in abuot a day of that so theres a fresh set in there now, Gapped to 50, Any ideas on what else i should try? Could part of the problem be that i got 3.73's trying to push 39.5's? ill have 5.13s in the rear this week.... If you need to know anymore pls ask, as this is making me stressed and very very pissed, i hold my self back everynight from Punching dents all over my truck to release anger, sorry so long winded, but im really fed up,
     
  2. Mr.Chevy4x4

    Mr.Chevy4x4 1/2 ton status

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    Sounds like you might have your valve lash too tight causing the intake valves not to close completely resulting in backfire. Is this the first run since rebuild or new cam installation?

    Mike
     
  3. Silver84k5

    Silver84k5 1/2 ton status

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    no not first run, this motor came in a Jimmy that i bought over a year ago, it hasnt been run too much since then It had approx. 25k on it when i bought it, i have put no more then 10k on it, prolly not even 10k, but it dogged like a SOB when i bought it, and its been doing this backfire crap for awhile Should i adjust the valves?
     
  4. Silver84k5

    Silver84k5 1/2 ton status

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    No one can tell me anything? pls help? TIA
     
  5. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    I'd adjust the valves to spec. It's free so there is nothing to lose but your time and it may cure the problem.

    I assume you used a timing light to check the timing?

    When exactly does it backfire? Under initial acceleration? Light throttle? Give us some specifics to work with.

    Do you have any ignition wires crossed? Easy to do with #3 and #5 IIRC.

    Rene
     
  6. leadfoot067

    leadfoot067 1/2 ton status

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    i would check the mechanical advance inside your distributor,make sure they are not froze up,they should move freely,if its froze your engine will be very doggy and it would cause backfire,you didnt mention in your post if you ever changed the distributor,hope this helps

    shane
     
  7. mudhog

    mudhog THEGAME Staff Member Super Moderator

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    like rene said make sure the wires are all correct i put a new engin in a friends bronco a few years ago and we had 2 wires crossed and it took a while to figure out i even checked them a few times and thought they were right but then found 2 that were crossed /forums/images/icons/shocked.gif /forums/images/icons/blush.gif just another thing to check
     
  8. 55Willy

    55Willy 3/4 ton status

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    Josh, sounds like timing and valve lash issues.

    the firing order is 1 8 4 3 6 5 7 2 and no more then 10 degrees at idle. i might be in portland wednesday getting a lift for a buddy if the scheduling is right i might drop by and get the meats and give you a hand.
     
  9. BurbinOR

    BurbinOR 3/4 ton status

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    Josh, more info needed such as when it is doing it..........on deceleration, accel, when?

    My thoughts - triple check the wires to make sure they are properly routed..........easy to cross one of them. Then make sure the wires are in good shape and are not cross firing. Cap/rotor OK? Plugs all look OK? Exhaust tight? An exhaust leak will allow it to backfire on decel................

    Double check the valves too. Might be leaving one open.

    Keep us informed so we can help ya.
     
  10. uglychevyZZ4

    uglychevyZZ4 3/4 ton status

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    Josh, if you are backfiring through the carb, you either have a timeing issue

    i.e.:bad advance pot, or bad advance weights possibly sloppy, flat cam lobe,

    OR it is a fuel problem

    i.e. : air leaking carb, grab the main rod that the butterflys are on, and see if it moves up and down /forums/images/icons/wink.gif if it does, its prolly a holly or a q jet, and its sukkin air, or is a valve cracked?

    these have been the MAIN backfire issue since ive been a master tech, like 10 years /forums/images/icons/wink.gif call me if you need any help or questions 253-653-5894, ill be home today workin on my 14 bolt.. and WHEN does it backfire? idle? hills? or when you goose it? impt question /forums/images/icons/smile.gif
    Rob
     
  11. TopOff

    TopOff 1/2 ton status

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    Flat cam...

    I was so PISSED when my friends new motor did this....

    I couldn't believe the cam flat spotted on two lobes. /forums/images/icons/mad.gif
     
  12. Silver84k5

    Silver84k5 1/2 ton status

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    If im at a stop sign and i stomp the gas like im trying to bark the tires, itll back fire, i checked the timing, OH yea heres something that happend also, when i went to grab the Dist cap, it shocked the hell outa me, when you say wires crossed its ok to have Wires crossed as in, They are going to the right plug just kinda crossed over eachother? i got brand new MSD wires, so those are all good, When we put new plugs in it, we ran it for awhile trying to get it to run right then the plugsd got fowl in no time, so some new plugs are in it again, ill check the valves as soon as i can find some of those Oil deflector things, timing is set at 8 im pertty sure, the plugs are gapped to 50...... I been thinking if the cam could have a flat lobe also, is that a PIA to check? thx for all responses, im gettin real frustrated here.......... Frank can i have your motor? ;]
     
  13. mudhog

    mudhog THEGAME Staff Member Super Moderator

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    </font><blockquote><font class="small">In reply to:</font><hr />
    when i went to grab the Dist cap, it shocked the hell outa me,

    [/ QUOTE ]
    i would start right there it should not do that /forums/images/icons/shocked.gif
     
  14. uglychevyZZ4

    uglychevyZZ4 3/4 ton status

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    1-are your plugs fuel foulin or oil foulin?
    2-smell em' or something,this is a good lead, sounds like you are either oil or fuel DROWNING them. you NEED to finger out if it is oil or fuel josh /forums/images/icons/shocked.gif
    3-is it one or all that are fouling?
    4-and if you are getting shocked, you may have a pin hole in a plug boot or wire, that will make it try to short on something, like YOU /forums/images/icons/laugh.gif pm me your #, ill call you if you dont have l/d.
     
  15. TopOff

    TopOff 1/2 ton status

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    Shouldn't the plugs be at 35?
     
  16. Silver84k5

    Silver84k5 1/2 ton status

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    When you put MSD in they say between 50-60
     
  17. Silver84k5

    Silver84k5 1/2 ton status

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    my buddy who is a pretty good mechanic was at my house, hes the one who said they sound like they are fowl when we pulled them he smelled them and didnt smell any oil, there shouldnt be any holes in the wires they are brand ****ign new
     
  18. k5blazerus

    k5blazerus 1/2 ton status

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    It could be that the distributor is 180 off from the firing order.
    Colin
     
  19. Leadfoot

    Leadfoot 1/2 ton status Premium Member

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    </font><blockquote><font class="small">In reply to:</font><hr />
    when i went to grab the Dist cap, it shocked the hell outa me

    [/ QUOTE ]

    That should NOT be happening. I would say that one of the new wires is faulty (or terminated incorrectly), or that you have a hairline fracture in the distributor cap. Remember even brand new items sometimes have faults. Either one of these can cause irratic ignition which could lead to backfiring through the carb.
    Hope this helps.
     

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