Compression test ??
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Compression test ??

  1. #1
    031 RIVER4FUN's Avatar
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    Default Compression test ??

    did a compression test on the 565 BBC. Should have done a leakdown but I didn't. 13 to 1 motor. All cylinders tested 200 to 210 except for #7, it was 240. Re-checked 3 times. Any ideas motor gurus?
    I may be growing older, but I refuse to grow up!

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    How does the valve lash on #7 compare to the others?

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    Quote Originally Posted by WETTE VETTE View Post
    How does the valve lash on #7 compare to the others?
    that was my first thought, exhaust valve opening late maybe. Lash was good at 024
    I may be growing older, but I refuse to grow up!

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    Boat Nut sleekcrafter's Avatar
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    any evidents of excess oil in the cylinder? leaky valve guide??
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    Is it a new motor? Its not uncommon for the lash to need adjusting after the first few runs then it should stay pretty consistent unless something is going south. What prompted the compression test?

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    031 RIVER4FUN's Avatar
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    Motor has 2 seasons on it. Ran at least 20 bottles of nitrous through it last summer [250 shot]. Tearing it down tomorro to check rings & bearings
    I may be growing older, but I refuse to grow up!

  9. #7
    Spiral out MikeF's Avatar
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    Quote Originally Posted by RIVER4FUN View Post
    that was my first thought, exhaust valve opening late maybe. Lash was good at 024
    I'm thinking the cam may have been made incorrectly (#7 intake lobe centerline a few degrees advanced.....for some unknown oversight).

    Intake closing is what initiates compression.

    Check it when you have it apart.

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    Quote Originally Posted by MikeF View Post
    I'm thinking the cam may have been made incorrectly (#7 intake lobe centerline a few degrees advanced.....for some unknown oversight).

    Intake closing is what initiates compression.

    Check it when you have it apart.
    I haven't personally seen this but it is a definate possibility.

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