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Max/Min PSI when using compressed air while changing valve seals.

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by Leadfoot, Jul 8, 2003.

  1. Leadfoot

    Leadfoot 1/2 ton status Premium Member

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    When changing valve seals and using compressed air to hold the valves closed, is there a min and max pressure to adhere to? I know too little pressure and the valve will drop in the cylinder, but what is the min pressure, and is there too much pressure (i.e. causing severe blowby at the rings)?

    Thanks.
     
  2. 88Silverado

    88Silverado 1/2 ton status

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    Hummm..good question.

    When I did mine, I just got a plug adaptor and connected it to my compressor. I had mine at around 100-120psi. no problem. Depending on how bad your rings are, most cylinders should be infe at 120psi. You only need enough to hold the valve firmly in place so you cant push the stem down releasing the pressure.
     
  3. DieselDan

    DieselDan 1/2 ton status

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    FWIW when I did the seals on my vette (twice now /forums/images/graemlins/frown.gif ) was to use the "rope trick." Instead of compressed air I would stuff a short length of nylon rope through the plug hole, then bar the engine 'til the piston came up to TDC (or pretty close). /forums/images/graemlins/thumb.gif
     

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