GM flywheel tooth count.
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GM flywheel tooth count.

  1. #1
    Member oldseddie's Avatar
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    Default GM flywheel tooth count.

    I am freshening up a SBC 400 for my fishing boat and have to replace the crankshaft due to rusty coupler splines from the out drive that used to live behind it. I recently replaced the starter with a top mount on my three point mount/bell housing. Since I have to have the crankshaft balanced I thought a change from a flywheel to a lighter flexplate would be in order. I don't intend to pull the engine until winter sets in. Does anyone know how many teeth are on the flexplate used with the top mount starter?

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  3. #2
    Senior Member tigertooth's Avatar
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    Coupler spines have nothing to do with the crank. The coupler bolts to the flyweel

  4. #3
    Member oldseddie's Avatar
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    No but on an outdrive it causes the input shaft to push on the crankshaft when trimming and that will take out the thrust surface. I have determined that indmar used a 168 tooth 14" flexplate with the three point mount bellhousing.


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  6. #4
    Senior Member tigertooth's Avatar
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    You are correct on the 168 tooth count. May want to check transom flex-engine alignment before reinstallation as input shaft should never make contact with crankshaft

  7. #5
    Member oldseddie's Avatar
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    How does one check engine alignment? I gave away my mercruiser alignment tool when I got back to a jet.

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    Senior Member tigertooth's Avatar
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    That tool you gave away is the only way I know

  9. #7
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    Chevy also used a smaller 153 tooth flywheel on some SBC....
    .

  10. #8
    Member oldseddie's Avatar
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    I retained the right to borrow it back if I need it. What is the program on using it. Do you temporarily mount the suction housing without the impellor shaft and adjust mounts till the tool rotates smoothly like a mercruiser out drive?




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  11. #9
    Senior Member andyc's Avatar
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    Default Starter

    Make sure the new starter your mounting on top is counter rotation too. 168 tooth internal balance I believe for the flywheel (no counter weight).

  12. #10
    Member oldseddie's Avatar
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    Already running the top mount starter. Don't want to go back to bottom mount. 400 sbc is external balance.

  13. #11
    Some guy obnoxious001's Avatar
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    Quote Originally Posted by andyc View Post
    Make sure the new starter your mounting on top is counter rotation too. 168 tooth internal balance I believe for the flywheel (no counter weight).
    If it's a stock 400 crank it is externally balanced, and different than a 454 counter weight if I am not wrong.

  14. #12
    Senior Member tigertooth's Avatar
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    Didnt realize you were putting the mercruiser motor in a jet. Pretty hard to align with 3 point mount. Up and down with an inclinometer. Side to side looking at 3 point flange alignment to jet housing or measureing off bellhousing bolts to sometbing on jet. Originally there was a tool that slid over the jet shaft and then it had a drill jig made into it to set tha front mounts. Havent seen one in over 40 years. Using that 3 point mount. Better make sure you have the right driveline length. Too short. You will bend the pump shaft. Too long. So long thrust bearing

  15. #13
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    Default 400/454

    Quote Originally Posted by obnoxious001 View Post
    If it's a stock 400 crank it is externally balanced, and different than a 454 counter weight if I am not wrong.
    Right, nothing about a SBC 400 and a BBC 454 are remotely the same.... While both are externally balanced, the external weights are totally different.... And not interchangeable...
    Ray
    LOUD BOATS SAVE LIVES

  16. #14
    Member oldseddie's Avatar
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    I should mention it has a 350sbc in her now but one of the vortex heads is cracked. I can't see throwing money at it when I have this 400 built by a NASCAR engine building buddy. We used the 153 tooth flywheel with the alpha out drive but it had a bottom starter. This engine pushed my heavy welcraft 60mph. Should push my new boat even faster since it weighs a ton less.


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