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Low compression???

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by or2play, Aug 9, 2003.

  1. or2play

    or2play 1/2 ton status

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    Did a compression check on my motor today. Its a 350 bored .040 with 67cc chambers. All the cylinders were in between 70 and 80 psi. My chiltons is telling me it should be 150 psi. I have some oily plugs so I decided to do the test. Expected to find a couple cylinders low. But seening how there all within 10 psi of each other I'm at a loss. The engine was rebuilt 3 years ago.
     
  2. BayouBlazer88

    BayouBlazer88 1/2 ton status

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    Yeah anything below 100psi is a big problem. Might be time for another rebuild and/or new block/engine. How does she run?

    And you said you have 67cc combustion chambers? Are those aftermarket heads or is that the stock combustion chamber volume for that year 350?
     
  3. or2play

    or2play 1/2 ton status

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    I have aftermarket heads, world s/r torquers. Just was out puting in new plugs and fuel filter. Also duing some tuning. Vacuum is reading 16 at idle. Don't get it. Motor has good throttle respones, sounds good. The only thing it does sometimes is going from a dead stop at large amounts of throttle it was hesatate. I need to find the stock combustion chamber size for this motor. I think they oftered 72cc and 64cc. Not sure thought.
     
  4. Confedneck

    Confedneck 3/4 ton status

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    maybe your compression rings have a problem?
     
  5. BayouBlazer88

    BayouBlazer88 1/2 ton status

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    I don't know about your year but I think my 88' 350 came with 76cc combustion chambers and so did almost every other 350. Those S/R torquers come with either 67cc or 76cc chambers.
     
  6. SUBFAN

    SUBFAN 1/2 ton status

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    Maybe your gauge is bad....
    Maybe the cam was installed a bit off....
    Something wrong with the timing chain....

    I am guessing there is something wrong with the cam timing,allowing the cylinder pressure to bleed out the exhaust....
    Do a leak down test, and see what that gives you....
     
  7. or2play

    or2play 1/2 ton status

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    Ya, I'll probably try the leak down test. Its weird, I put good plugs in, changed the fuel filter, and did some minor tweaking to the carb. Took it for a drive, runs great now, better than before. Just don't seem like it has low compression. I guess time will tell. In a week or so if its still running good, I'll do another compression test. There is a chance I messed up. I only hand tightened the tester down.
     
  8. Seventy4Blazer

    Seventy4Blazer 3/4 ton status

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    use the low compression to your advantage, slap a blower on the damn thing....
    oh, and the next time i pass you on the way to work, WAVE BACK FUKR! /forums/images/graemlins/rotfl.gif
    Grant
     
  9. or2play

    or2play 1/2 ton status

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    Hey, I didn't even know it was you until you were by me. I waved then, but you were long gone. Just its early in the morning and I'm driving to work doesn't mean that I'm awake yet.
     

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