Homemade leakdown tester

Discussion in 'Tips 'n' Tricks Topic' started by COPO, Sep 3, 2015.

  1. COPO

    COPO Veteran Member Lifetime Gold Member

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    [​IMG]

    Don't forget the .040 orifice. You can get the drill bit from a hobby store. Fill 1/4"-1/2" with JB Weld. My orifice is in the connection just before the RH gauge.
     
    Last edited: Sep 3, 2015
  2. l16pilot

    l16pilot Veteran Member Lifetime Gold Member

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    Mark - What do you use to hold engine at TDC for each cylinder?
     
  3. COPO

    COPO Veteran Member Lifetime Gold Member

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    Once the piston is at TDC and slowly add the air with the regulator, the piston does not move. Leave the trans is neutral. I used a camera inside the spark plug hole to make sure it was at TDC so the valves are closed. Before I used to loosen all the rockers so I knew the valves were closed and I still used a camera to get the piston at TDC, but then I would have added time to set all the hyd lifters which I'm not thrilled about. I'd rather set solid lifters cause there's no up and down and spinning of the push rod BS. :)
     
  4. onovakind67

    onovakind67 Veteran Member

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    Will my motor have more leakdown if I use a .030" drill?
     
  5. COPO

    COPO Veteran Member Lifetime Gold Member

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    The results will be the same even if you use a smaller drill. The leakage will just come out SLOWER on the RH gauge that's connected to the cyl than if you use a .040. The .030 drill is smaller. If you used for example a 1/16" or 1/8" drill bit to make your hole, and regulated 100+ PSI into the both gauges, then adjusted the L to 100 PSI, the R gauge would be leaking so fast that you wouldn't have time to see what the reading was.

    I use my compression gauge hose but unscrew the shraider valve when I use it for the leakdown test.
     
    Last edited: Sep 5, 2015
  6. onovakind67

    onovakind67 Veteran Member

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    It would be just the opposite. You are comparing the pressure drop across the hole to the pressure drop across the leaks in the cylinder. A larger hole would result in the RH gauge reading higher, and your leakdown would appear to be smaller. That's why the size of the hole matters, and there is no real standard for that. I would use a rotameter.
     
    Last edited: Sep 5, 2015
  7. COPO

    COPO Veteran Member Lifetime Gold Member

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    The STD is .040. Search Google on orifice hole on leakdown testers. I didn't make it up.
     
  8. l16pilot

    l16pilot Veteran Member Lifetime Gold Member

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    Thanks Mark :)
     
  9. COPO

    COPO Veteran Member Lifetime Gold Member

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    You bet. And it doesn't matter if the JB weld is on the L or R side of the pipe when you go to assembling it.
     
    Last edited: Sep 5, 2015

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