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  1. #1
    Member chevyaddict's Avatar
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    1968 Convt, 1990 Convt

    Default Very Strange Phenomena - Need Advise

    Hi all;
    I have a strange phenomena happening. We are working on a 302 (bored to a 306) Ford motor. Fast! At idle, you can put your hand on the #7 cylinder and its cold and also at steady rpm it seems to be misfiring as well out of #7. Here are all the things we've tried so far and none of them have remedied the problem:

    1. Checked/switched around plugs and wires - no change.
    2. Switched with a new distributor - no change.
    3. Messed around with different carb settings and jets (its a 670 Holley) - no change.
    4. Ran a compression check in the cylinder - no problem.

    Now under acceleration, the tube starts to get hot and when you are on it, it runs like a dream. However, it is misfiring under no load. WHY? At this point we are thinking its something with the manifold. Here is the manifold that is being used:

    http://cgi.ebay.com/ebaymotors/Typho...86917676QQrdZ1

    What else is there to check? Any thoughts???
    Dawn
    2 Corvettes, 3 Camaros (89 IROC Convt; 76 Dragcar; 71 RS), 2 Trucks (68 Shortbed & Dually), 66 Corvair, & ZX6R Kawasaki Ninja!!
    Chevyaddict to the core!

  2. #2
    Member gmjunkie's Avatar
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    Nov 2004
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    Old Fort NC/Vero Beach FL
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    Corvette(s)
    03 Z-51,78 L82 Coupe

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    Valve adjustment,(Some 302's are adjustable,Depending on year)Weak Valve spring,Bent valve,Cracked head,Vacuum leak at intake runner!!
    Quote Originally Posted by chevyaddict View Post
    Hi all;
    I have a strange phenomena happening. We are working on a 302 (bored to a 306) Ford motor. Fast! At idle, you can put your hand on the #7 cylinder and its cold and also at steady rpm it seems to be misfiring as well out of #7. Here are all the things we've tried so far and none of them have remedied the problem:

    1. Checked/switched around plugs and wires - no change.
    2. Switched with a new distributor - no change.
    3. Messed around with different carb settings and jets (its a 670 Holley) - no change.
    4. Ran a compression check in the cylinder - no problem.

    Now under acceleration, the tube starts to get hot and when you are on it, it runs like a dream. However, it is misfiring under no load. WHY? At this point we are thinking its something with the manifold. Here is the manifold that is being used:

    http://cgi.ebay.com/ebaymotors/Typho...86917676QQrdZ1

    What else is there to check? Any thoughts???
    junk!!
    "WARNING"
    The views and opinions of this forum user might not be suitable for others, this user may appear to be heavily over-medicated, under medicated, intoxicated, listening to the voices in his head or just plain being an ass, so some viewers may be offended!~!!!
    www.gmjunkie.com
    Founding Member: 10 Corvettes Anonymous


  3. #3
    Member chevyaddict's Avatar
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    Default

    Quote Originally Posted by gmjunkie View Post
    Valve adjustment,(Some 302's are adjustable,Depending on year)Weak Valve spring,Bent valve,Cracked head,Vacuum leak at intake runner!!
    Well, the motor only has about 6000 miles on it (or less) and was professionally built. Wouldn't a weak valve spring or bent valve show up in the compression check? We've checked the vacuum - seems to be fine and I doubt its a cracked head... the car runs too good and fast under load.........

  4. #4
    Member gmjunkie's Avatar
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    Old Fort NC/Vero Beach FL
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    03 Z-51,78 L82 Coupe

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    Quote Originally Posted by chevyaddict View Post
    Well, the motor only has about 6000 miles on it (or less) and was professionally built. Wouldn't a weak valve spring or bent valve show up in the compression check? We've checked the vacuum - seems to be fine and I doubt its a cracked head... the car runs too good and fast under load.........
    It should!!! It could have a Casting Flaw in the Intake on #7 runner, or the Intake gasket it self at head!! Depending on where the crack in a head might be would determine if it would change compression or not!!
    junk!!
    "WARNING"
    The views and opinions of this forum user might not be suitable for others, this user may appear to be heavily over-medicated, under medicated, intoxicated, listening to the voices in his head or just plain being an ass, so some viewers may be offended!~!!!
    www.gmjunkie.com
    Founding Member: 10 Corvettes Anonymous


  5. #5
    geekinavette's Avatar
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    Aug 2002
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    Colorado Springs, CO USA
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    1,805
    Corvette(s)
    84 Z51 auto R.I.P. Current 89 black roadster

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    Does it use hydraulic lifters? I've seen a lifter do weird stuff like that.

    Bill

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