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Thread: Help!!backfire problem

  1. #91
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    May 2008
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    IMO, compression and leakdown should have been the first things done...

  2. #92
    Join Date
    Dec 2009
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    houston tx
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    Quote Originally Posted by CHEVROLADE View Post
    yea it still backfires in park...i even moved the maf right in front of the tb....the back fire is out the intake ...can hear it clear out the cold air.loud .....

    if any of u can break me down a compression test procedure for the ls1s..ill do it right now and get some readings...appreciate all of yall tips and info..
    get a hold of peewee he knows how to fix it.

  3. #93
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    Jan 2008
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    i just did the compression test

    90 --- 165
    155 --- 180
    180 --- 180
    180 --- 180
    ^^
    FRONT OF ENGINE
    Last edited by CHEVROLADE; 07-22-2011 at 10:11 PM.

  4. #94
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    Ouch!!!! If you have access to compressed air then do a quick check and see what the problem is. Take the rockers off the three problem cylinders and hook the air up to each one. You will be able to hear where the problem is. Either leaking from exhaust, intake, or crankcase. Number 8 is definately hurt.

  5. #95
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    Looks like the #8 ringland got lifted and particles probably got hung on the valves on #6 and #7.

  6. #96
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    Jan 2008
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    ok cool,i will do that in the morning for sure im tearing into it...this is frustrating
    funny how its not running 100% but still pulled a new 5.0 stang on my 22s haha

  7. #97
    Join Date
    Dec 2006
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    4,127
    take the advice from Jon hes more then likely right, which valves you running? if they are the stock l92 valves ( truck ) you more then likely floated one and hit the piston, there not designed for high rpms, you need the ls3 valves the hollow stem and sodium filled then again id go with ferrea valves
    Simple: 408 on steroids!
    single digits coming soon!

  8. #98
    Join Date
    Nov 2007
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    Pittsburgh, PA
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    head gasket....if you look at the reading 6 and 8 are low. take a look at the gasket when you pull the heads and see is there was any signs that it was leaking between the two cylinders

    your back firing is you trying to fire coolant!!!! i told you to show your plugs and look carefully for a coolant ring on them.
    2002 Lightning - GT headed 5.5Litre w/ Twin 7665s
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    it ain't that I'm too big to listen to the rumors, It's just that I'm too damn big to pay attention to 'em..That's the difference

  9. #99
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    Dec 2006
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    Quote Originally Posted by Quik View Post
    head gasket....if you look at the reading 6 and 8 are low. take a look at the gasket when you pull the heads and see is there was any signs that it was leaking between the two cylinders

    your back firing is you trying to fire coolant!!!! i told you to show your plugs and look carefully for a coolant ring on them.


    yeah it would have been good to see the plugs, to see if their were a coolant splatter or ring, but oh well im sure we'll hear something soon!


    good luck zach!
    Simple: 408 on steroids!
    single digits coming soon!

  10. #100
    Join Date
    Jan 2008
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    these the ones i need? are they a direct swap? http://www.lingenfelter.com/mm5/merc..._Code=12569427 i cant find the exhaust valves...i will pull the heads soon,while there off ill do the valve upgrade..if its a piston ,engine will get pulled...shoot a complete ls3 head is only 375.00

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