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  1. #1

    leak down, positive or negative pressure

    so all the vids on youtube and the discussions on here seem to say put negative pressure on your engine (vaccuum around 9 pounds) and check to see if it holds. I just spoke with John at Watcon and he said he always does positive pressure, by pumping it up. So whats the deal with the vacuum? Is this essentially doing to the same test just with a different pressure/vaccuum?


  2. #2
    BlueFishCrisis's Avatar
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    I would imagine it is the same thing, but you don't need to mechanically attach anything to seal the exhaust and intake manifolds. With vacuum, the negative pressure holds whatever you are sealing it up with in place.

  3. #3
    Derwood98's Avatar
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    Vacuum is nice because it pulls the blank offs against the sealing surfaces. You would need a more ridgid material for blank offs if using positive pressure. The nice part about using positive pressure is that you can use bubbles to locate your leak if you have one.

  4. #4
    gotcha. I'll have to try and find some thick rubber laying around to make seals, or maybe gasket material at napa or autozone should work

  5. #5
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    I made plates out of 3/8 clear acrylic and seal them down with some RTV. When Im done, I peel the plates off and the RTV cleans off easily.

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