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Just did compression check...help with results!!

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by Waxer, Mar 19, 2000.

  1. Waxer

    Waxer 1/2 ton status Author

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    ok, here are the numbers as follows
    before oil after adding oil
    Cylinder---PSI Cylinder---PSI
    1--118| |1--122
    2--125| |2--130
    3--108| |3--116
    4--130| |4--135
    5--135| |5--150
    6--120| |6--125
    7--135| |7--145
    8--118| |8--125

    On each check, the compression started out somewhat lower on the first compression stroke, then after 3 more (which the haynes manual says to do 4), the compression got a little higher and leveled off at what you see above.

    Any help would be appreciated. Haynes manual says the compression should be at 150psi and no greater differences between cylinders of 20psi. Thanks
     
  2. Corey-88K5

    Corey-88K5 1/2 ton status

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    Home: Michigan, Stationed: Hill AFB (Home of Moab.
    If all you are worried about is compression, you could get a valvejob, and hone all the cylinders & re-ring. By no means a inexpensive jaunt, or quick, but if you are worried about it, seems to be the least expensive way. Than there is always a rebuild...

    Hey, didn't you just build/purchase a/this motor?

    Corey
    88K5

    [​IMG]<font color=blue>Girls Like Guys In Bow Ties</font color=blue>
    <font color=red>http://www.geocities.com/corey_perez
     
  3. Jason73K5

    Jason73K5 1/2 ton status

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    It looks like your engine is a bit on the worn side. A compression test is a good indicator of where you're having problems, but just because you're a little on the low side on some of your cylinders it doesn't mean that you have to rebuild the enging right now. Your compression numbers didn't change dramatically after the oil, even though they did go up some. If the engine still runs fine, then I'd say don't do anything to it untill you start having problems, save up for a crate motor if you can! If you are having problems, the cheapest fix would be a re-ring and valve job. I hope this helps you a bit. Good luck with whatever you choose.
     
  4. Waxer

    Waxer 1/2 ton status Author

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    Corey, no I didnt just replace it. This motor came with the K5 when I bought her a couple years back. I did replace the tcase with a 205. Maybe thats what your thinking of.
     
  5. IDGMC

    IDGMC 1/2 ton status

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    What i've heard is that if your numbers on a compression test are all within 10% your in pretty good shape.
     
  6. Blazer1970

    Blazer1970 1/2 ton status

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    I wouldn't worry too much about those numbers. Do you have a problem with the way the truck is running?

    Tim

    1970 Blazer CST 4X4 350 SM465 NP205
    1987 Suburban 4X4 350
    1988 Chevy Pickup 4X4 350
     

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