The one I have looks like the second picture but not as nice as the Longacre one unfortunately. Only, the second gauge is marked (clockwise) 100, 90, 80, 70... in 5% increments. So you fill the gauge and combustion chamber with compressed air then use the regulator to dial the second gauge to "0", or 100 as on the Longacre gauge, then read the leakdown.
One issue is that my guage operates at 10-20 psi when performing the test, not 100 psi. I don't know if this would exacerbate a leaky ring due to a lack of pressure to "seat" the ring or return a faulty reading due to a lack of pressure to force the leak? Or, make no difference at all??
All leakage is heard in the crankcase (rings) when using a hose/stethoscope arrangement. Intake and exhaust are pretty quiet except for what is likely ambient noise.
Now I have a whole new set of questions and will have to double check my readings with another gauge I think.
