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Thread: zilch for compression on #1
          
   
   

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  1. 10-01-2015 09:17 PM #1
    TOW'D
    TOW'D is offline CHR Member/Contributor
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    zilch for compression on #1

     



    Hi Gang,
    I did a compression test on a GMC 7.4L in a pleasure boat.
    All except #1 were close to 180 psi
    #1 was zero
    I put the crank on #1 TDC and put shop air into spark plug hole and we can hear air leaking out the throttle body.
    Today I pulled that head off .
    The exhaust valve looks like it has a nice shiny surface where it seats but the intake doesn't.
    All the push rods look good.
    I'll do a valve grind.

    my question
    Are the head bolts reusable?
    thanks
    Hank
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  3. 10-02-2015 08:51 AM #2
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    stovens
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    Not sure Hank, but here to hear, what others will say. Just a thought but could it be a cam lobe issue, or just not seating properly?
    " "No matter where you go, there you are!" Steve.
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  4. 10-02-2015 10:31 AM #3
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    rspears
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    Are you asking because of the widespread discussion about Gen II and newer head bolts being TTY because they spec an initial low torque, followed by an angular final tightening in sequence?
    Roger
    Enjoy the little things in life, and you may look back one day and realize that they were really the BIG things.
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  5. 10-02-2015 03:29 PM #4
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    jerry clayton
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    7.4 are reusable
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  6. 10-02-2015 08:43 PM #5
    TOW'D
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    thanks guys
    I tested the head with water resting in the combustion chamber and it leaked past the intake valve on #1
    yes I was wondering about the TTY bolts good to know they are Not used

    cheers
    Hank
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  7. 10-13-2015 08:40 AM #6
    TOW'D
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    What kind of thread sealant do you guys use on the head bolts ?
    It seems that the shorter bolts are exposed to the antifreeze.
    thanks
    Hank
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