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Thread: motor rocks too much at idle

  1. #1
    Senior Member MASTER BUILDER
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    motor rocks too much at idle

    big block just rebuilt wiyh yhe best rotating assembyy, balanced, real big lunatti solid roller,stock chevy dual plane, aluminum heads, stock fuel pump and lines, headers through mufflers, msd ignition, roller roch=kers. all good stuff. the motor rocks like crazy at a normal idle(800rpms), and and as 1200 idle it still rocks too much. the car does not have a miss init when running, but has a little vibration on takeoff (its a 4 speed car, with new clutch pressure plate and flywheel. something is very wrong. any ideas out there in chevyland. could it be valves adjusted wrong(i hear a few loose ones). guy says the vacuum reading is good( i dont believe him asd the cam is a big, big cam). this is the second carb on the car with no change. HELP chevy arPS i dont think there is any typeof cranckcase evacuation system or no type of pvc vale from valve cover to vacuum side of carb.

  2. #2
    Senior Member EXPERT BUILDER gearhead1011's Avatar
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    the flywheel could be "clocked" wrong if it's externally balanced.

  3. #3
    Senior Member DYNO TECH
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    harmonic balancer wrong?

  4. #4
    Senior Member RACING JUNKIE
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    Re: motor rocks too much at idle

    Quote Originally Posted by chevyart
    , real big lunatti solid roller,stock chevy dual plane, . the motor rocks like crazy at a normal idle(800rpms), and and as 1200 idle it still rocks too much. .
    You said it's a A big solid roller... and you think it should idle at 800-1200 rpm? :? Does it smooth out if you idle it up a bit more?
    What are the cam specs?

  5. #5
    Senior Member DYNO TECH
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    Re: motor rocks too much at idle

    Quote Originally Posted by Tod74
    Quote Originally Posted by chevyart
    , real big lunatti solid roller,stock chevy dual plane, . the motor rocks like crazy at a normal idle(800rpms), and and as 1200 idle it still rocks too much. .
    You said it's a A big solid roller... and you think it should idle at 800-1200 rpm? :? Does it smooth out if you idle it up a bit more?
    What are the cam specs?
    Ditto?
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  6. #6
    Senior Member MASTER BUILDER
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    cam size in engine that rocks

    my buddy said the cam is about 285 and 290 duration advertised duration and just a little over .600 lift. I guess this is a big cam by my standards, but to you guys out there maybe not. does this size cam cause the enging rock I described. thanks chevy art

  7. #7
    Senior Member RACING JUNKIE
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    In my opinion you should not let a solid roller idle that low for too long anyway...it is hard on the lifters. Speed the idle up to 1500 or so.

    jmo

  8. #8
    Senior Member RACING JUNKIE curtisreed's Avatar
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    C A,

    I don't think the cam size is the problem, that cam is right about the size I have in my 383 sbc. 282/290 .600/.640 106lca. My motor will idle at 800rpm in gear with no problem if I wanted it to. Does it seem like the lope of a race engine or a constant shake. Could it be the wrong balancer and flexplate/flywheel, internal on external engine?

    Curtis

  9. #9
    Senior Member MASTER BUILDER
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    rockin engine

    its not the lopey idle like a race engine. it shakes. its external balance. he re-used a fluiddamper instead of getting a new one. the flywheel and pressure was supposedly clocked correctly(supposedly) when installed. this was the first suspicion of the guy with the blue race car(first reply) it was a good guess and could still be a possibility. any other ideas out there thanks chevy art

  10. #10
    Senior Member RACING JUNKIE
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    It has to have a flywheel made for external balance.


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