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  1. #1
    Join Date
    Feb 2006
    Salisbury, MD, USA

    Default "HI, I've been told tha


    I've been told that a reasonable check of engine condition in lieu of compression testing is to measure its "blow-by" with an instrument. What is engine "blow-by", and what type of instrument is used?

    Thank you,


  2. #2
    wasco's Avatar
    wasco Guest

    Default blow by is refering to the com

    blow by is refering to the compression gases being forced into the crankcase on compression / detionation stroke due to worn rings or scored cylinder bores.
    Have never heard of any test to analize a engines condition by measuring blow by though.
    I suppose if a engine is in really bad shape a visual would be a dead give away. But no substitute for a compression test!

  3. #3
    poker casino190's Avatar
    poker casino190 Guest

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  4. #4
    poker casino190's Avatar
    poker casino190 Guest

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  5. #5
    Join Date
    Apr 2006
    , Langkawi, Malaysia

    Default "Theese kind of test instrumen

    "Theese kind of test instruments were available some years ago, from amongst BOSCH. It worked the way that the injector was replaced with an air hoose connected to a small compressor and a flow meeter. In the instructions following the instruments there were given roughly how much flow was acceptable. By blowing soap water in the innlet/exhaust ports, valve shafts etc leakage could be determined. Have not seen any one in operation in the last decade and never at a marine shop! Quite expencive and not very accurate."

  6. #6
    scott s.'s Avatar
    scott s. Guest

    Default "cylinder leak down tester doe

    "cylinder leak down tester does not replace compression test. rather, it helps locate source of compression loss by pressurizing cyl. @ T.D.C. of compression stroke, and measuring flow from intake, exhaust, & crankcase. (valves, & rings) available from Snap-on. expensive, & rarely needed"

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