Engine Vibration
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Engine Vibration

  1. #1
    Strap on the JATO konajet74's Avatar
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    Default Engine Vibration

    Hey guys, the fun continues......I had my BBC 454 crank balanced
    along w/ the rods & pistons. I added a internal balance damper/
    flywheel combo & the thing vibrates like hell?? At idle it's not
    noticeable, but at the rpm's go up it's felt throughout the boat,
    thru the steering wheel and the floor. I first thought it was the
    pump. I disconnected it from the motor & it's still there. What
    the hell?? Can I put the external balance damper/flywheel back
    on, or will that not work since the cranks had mallory added to it?
    If, since the crank has been (supposedly) internal balanced, will
    the external balanced combo cancel each other out? What else
    could cause this or has anyone had this scenario before??

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    21 Daytona Outlaw's Avatar
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    sounds like you still need an external damper. and an external balanced flywheel/flexplate
    Last edited by Outlaw; 11-05-2008 at 04:37 PM. Reason: spelling
    #55

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    Strap on the JATO konajet74's Avatar
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    Now you really have me thinking...... The machine shop told
    me otherwise, along w/ other issues I've had with this machine
    shop.

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    E-7 Sheepdog (ret) SmokinLowriderSS's Avatar
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    After the third read, I THINK I understand, seemed contradictory at first.

    The machine shop MAY have balanced it with the intention of external balance parts added on (the harmonic dampener and flywheel/flexplate).

    Did they add slugs of mallory metal to the crank?
    If they did, that is usually only done to a full internal balance job as far as I know.

    If they did not, you have the wrong external parts on it.

    First step is pull the pan off I look the crank over.
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  7. #5
    gn7
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    did the machine shop have your damper and flywheel when he balanced it?
    Are you absolutly certain the damper and flywheel you have are NOT COUNTER WEIGHTED?
    Did you actually see mallory in the crank? Most BBC take two slugs in the front and at least one in the rear of the crank.



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    Strap on the JATO konajet74's Avatar
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    Quote Originally Posted by gn7 View Post
    did the machine shop have your damper and flywheel when he balanced it?
    Are you absolutly certain the damper and flywheel you have are NOT COUNTER WEIGHTED?
    Did you actually see mallory in the crank? Most BBC take two slugs in the front and at least one in the rear of the crank.
    they did not want the damper/flywheel when balanced. Both the damper
    & flywheel are for internal balanced engines. The crank has 1 spot where
    there's welding/mallory added? Do they sometimes balance the crank for
    using external balanced damper/flywheels?

  9. #7
    Strap on the JATO konajet74's Avatar
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    Quote Originally Posted by Outlaw View Post
    sounds like you still need an external damper. and an external balanced flywheel/flexplate
    Can this be done after the work on the crank?

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    21 Daytona Outlaw's Avatar
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    Quote Originally Posted by konajet74 View Post
    Can this be done after the work on the crank?
    here is a good read,

    http://www.circletrack.com/techartic...ogy/index.html
    #55

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    Senior Member H20MOFO's Avatar
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    IMO you need to call the guy that balanced it and ask him again. If he says you should be running a balancer/flexplate for an internal deal, and you are, and you have a vibration, you've got a problem. I have a hunch Outlaw and Smokin hit the nail.
    Another Hot Boat refugee

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    Cantard 71hallett's Avatar
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    I have the feeling the balanced it internaly as in they didnt drill the flywheel and or the balancer but did the balancing by working on the crank. Bet you need the external stuff still.
    Quote Originally Posted by gn7 View Post
    It would be a balmy 85* in Steel's shop if he would move a little faster

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    Strap on the JATO konajet74's Avatar
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    Here's another question I'm confussed about....All damper/flywheel's
    that are externally balanced have the same amount of weight added
    to them, am I right? Anyone know how much is added to each item?
    So, since my crank was balanced would it make it better than a stock
    crank w/ external balanced damper/flywheel added?

  14. #12
    Cantard 71hallett's Avatar
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    Lots of shops balance an external balance engine internally so if you ever have to change the balancer/dampner or flywheel you dont have to re balance the engine. Its kind of hard to say balanced crank..... rods pistons exc. are all part of this.
    Quote Originally Posted by gn7 View Post
    It would be a balmy 85* in Steel's shop if he would move a little faster

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    Distinguished Member David 519's Avatar
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    If the shop did not want the flywheel/damper, that implies the crank was supposedly internally balanced. If it only has one slug of heavy metal on one end, it was likely balanced wrong and why it shakes. Since you're not sure what's up, talk to the shop. Seems you have concerns with their work so it's likely you'll have to pull the engine apart and start over. The likelyhood you could simply throw an externally balanced flywheel and damper on and have it work are slim to none. Sorry...
    Quote Originally Posted by gn7 View Post
    ....... David 519 is 100% correct........

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    Senior Member wagspe208's Avatar
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    1) get a new REAL machine shop to do your work
    2) 1 slug is not enough to internally balance a stock 454 type crank unless you are using featherweight components (still don't know if it would work..maybe SBC weight stuff)
    Probably needs to have external weighted stuff on it. Back to half assed shop.

    3) Guys will argue internal vs external all day. Personally I am an internal guy. Change flywheel, balancer, etc, no issues. Extenal stuff is to a factory spec. Change an external balanced flywheel with another, you just wasted your money spent on balancing. You are back to factory spec close is good enough.
    Wags

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