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Thread: blow by

  1. #1

    blow by

    i have a sbc 408 with lot of blow back pressure, motor is kind of new just been together for 3 months lot of white smoke coming from breather cap what could this be thanks

  2. #2
    Administrator RACING JUNKIE bjuice's Avatar
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    Its oil getting past your rings..some HP Race motors are built loose and could possible have some minor blow by....thats why a vaccum pump is highly recommended/required..

    if you do not have $600.00 to invest in a vaccum pump..at least install some e-vac tubes in the headers

    hard to tell by internet how bad your blow-by is...so i am just making a general statement here..

    but its oil getting thru

    Brian
    Bjuice..

    "I'M YOUR HUCKLEBERRY ! "

  3. #3
    Senior Member RACING JUNKIE
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    White smoke may indicate a water leak, being it's a 400 blk. they are notorious for blown head gaskets. Have you noticed any milking of the oil?

    JMO

    Zip.

  4. #4
    no water in oil thanks

  5. #5
    Senior Member EXPERT BUILDER
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    400 blocks if they are not plate honed with the same hardware it will show alot of blow by and if your building a lot of cylinder pressure its even worse.

    Do a leak down test.
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  6. #6
    ok compression check #1-190, #3-135,#5-0, #7-230, #2-220, #4-225, #6-220, #8-230 could it be rings or head problem

  7. #7
    Senior Member EXPERT BUILDER
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    Quote Originally Posted by arobunson
    ok compression check #1-190, #3-135,#5-0, #7-230, #2-220, #4-225, #6-220, #8-230 could it be rings or head problem
    You really need to do a leak down test!!!!!!!!
    WWW.CNCBLOCKSNE.COM
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  8. #8
    Senior Member RACING JUNKIE
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    Take the head off on the drivers side, the problem should be quite evident since you have "ZERO" compression on number 5 cylinder.
    My money has it that you have a hole in the top of your piston.
    Goodluck, Charles
    ***IN GOD WE TRUST***

  9. #9
    Senior Member EXPERT BUILDER
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    Quote Originally Posted by arobunson
    ok compression check #1-190, #3-135,#5-0, #7-230, #2-220, #4-225, #6-220, #8-230 could it be rings or head problem
    You maybe looking at a bent valve!!!!!!
    WWW.CNCBLOCKSNE.COM
    IS A DIVISION OF
    HINKSON AUTOMOTIVE
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    EMAIL CHINKSON@JUNO.COM

  10. #10
    Senior Member RACING JUNKIE
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    re; blowby

    I once forgot to install the #5 piston, but I knew right off, somthing was amiss, rod made a terrible clatter.

  11. Racing Junk


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