"Rod Bearing Clearance"
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"Rod Bearing Clearance"

  1. #1
    JRPM/e-PerformanceMarine Squirtin Thunder's Avatar
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    Default "Rod Bearing Clearance"

    Well we started assembling the 466 back up motor for our Comp Jet boat. Installed the cam, everything was good. We measured the crank main journals and that came up perfect. So then we put the main bearings in and installed the crank, so far so good. Well I know I should have checked the rod journals when it was on the bench, but I took it for granted that they would be right. They are 2.486 and they should be 2.500 or 2.490 or even 2.480. This sucks !! What do you guys recommend I do ?

    Thank you
    Jim
    Jim & Amanda Rich
    CJ 72 & 53c

    JR Performance Motorsports

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    LP-25.com Infomaniac's Avatar
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    Check the actual bearing clearance before making a decision.
    If For Some Reason I Do Something Worthy Of Recognition. God Provided The Ability And Deserves The Credit.


    QE 439 Twin Turbo

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    Senior Member GT Jets's Avatar
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    Quote Originally Posted by Squirtin Thunder View Post
    Well we started assembling the 466 back up motor for our Comp Jet boat. Installed the cam, everything was good. We measured the crank main journals and that came up perfect. So then we put the main bearings in and installed the crank, so far so good. Well I know I should have checked the rod journals when it was on the bench, but I took it for granted that they would be right. They are 2.486 and they should be 2.500 or 2.490 or even 2.480. This sucks !! What do you guys recommend I do ?

    Thank you
    Jim
    Dumb question #1.....Are all eight journals the same?

    Dumb question #2......What were they supposed to be?

    Dumb question #3....Did you use more than one micrometer (that one has bitten me more than once...)

    IMHO you are too far from using a +.001 or +.002" bearing (and too far from .010, .020 obviously)...

    The only two options I could come up with are custom bearings or a do over...Sucks for sure..

    GT
    GT


    Quote Originally Posted by Quickjet View Post
    Put a 300 on the back of it, Flywheel it and a nosecone. $15,000 later you'll have a 65 mph pile of shit......

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    JRPM/e-PerformanceMarine Squirtin Thunder's Avatar
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    Quote Originally Posted by GT Jets View Post
    Dumb question #1.....Are all eight journals the same?

    Dumb question #2......What were they supposed to be?

    Dumb question #3....Did you use more than one micrometer (that one has bitten me more than once...)

    IMHO you are too far from using a +.001 or +.002" bearing (and too far from .010, .020 obviously)...

    The only two options I could come up with are custom bearings or a do over...Sucks for sure..

    GT
    DQ 1) exactly
    DQ 2) 2.500
    DQ 3) 3

    This is a 460 BBF. I bet it is cheeper to cut the crank down than get custom bearings.
    Jim & Amanda Rich
    CJ 72 & 53c

    JR Performance Motorsports

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    JRPM/e-PerformanceMarine Squirtin Thunder's Avatar
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    Quote Originally Posted by Infomaniac View Post
    Check the actual bearing clearance before making a decision.
    I am going to do that right now.
    Jim & Amanda Rich
    CJ 72 & 53c

    JR Performance Motorsports

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    Senior Member GT Jets's Avatar
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    Quote Originally Posted by Squirtin Thunder View Post
    DQ 1) exactly
    DQ 2) 2.500
    DQ 3) 3

    This is a 460 BBF. I bet it is cheaper to cut the crank down than get custom bearings.

    Me too....

    GT
    GT


    Quote Originally Posted by Quickjet View Post
    Put a 300 on the back of it, Flywheel it and a nosecone. $15,000 later you'll have a 65 mph pile of shit......

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    Senior Member lbhsbz's Avatar
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    Is it a new crank?...if so, I'd have a call into the manufacturer to see what they were smokin when they ground the journals.

    If it's used...looks like a .010 under with some wear that's been polished a couple too many times.

    Grind it .020 under or get a new one.

  10. #8
    JRPM/e-PerformanceMarine Squirtin Thunder's Avatar
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    Quote Originally Posted by lbhsbz View Post
    Is it a new crank?...if so, I'd have a call into the manufacturer to see what they were smokin when they ground the journals.

    If it's used...looks like a .010 under with some wear that's been polished a couple too many times.

    Grind it .020 under or get a new one.
    Nope this is an old crank. It was unmarked by the previeous grinder. I will have to pull it and cut it .020 under no biggy just money right? I forgot when we pulled it apart it had .010 bearings in it and they were loose as a goose, as you get older it seems like you forget little things.
    Jim & Amanda Rich
    CJ 72 & 53c

    JR Performance Motorsports

  11. #9
    Hat
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    a good crank grinder can fix it, thats .006 to fix, not that big a deal, but make sure they know what they are doing, look at other cranks they do, and see if the Radius is smooth, it it's rough...take it someplace else....and make SURE they use a radius tool to dress the stones, if the uses a hand stone...keep shoping I have always ground my stuff on split, put the bearings in the rods torq them in a fixture and measure the rod breaing I.D. then grind the crank to give what you need...I keep as much crush on bearings as possible, the crush pushes the bearing to fit the housing, if theres not a lot of crush the bearing can begine to move if it loses much more crush it will fail because of heat transfer cant be enough and the material begins to simply over heat, curling the bearings at the parting line, now it's a scaper and peels off the oil and kills itself.
    Last edited by Hat; 01-12-2010 at 04:15 PM.

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