[71cadc10]

question, are you taking the leakage test with the cylinder under test at TDC ?

I ask because your lowest readings show 5 & 8 which are sister cylinders and both would be at TDC (or BDC) at the same time.

like you noted, the main way air can get from chamber to intake manifold, is intake valve path. However, if the PCV hose is hooked up to intake, this could allow some more to get to the intake from the crankcase. Air bleeding by the ring gaps would then push up thru the PCV and you may hear it in the intake. If this is the case, you should hear it on all 8.

Another check could be remove the intake manifold...pressure up and spray some soapy water directly down the port to see if the intake valve is sealing. You'll get bubbling if the valve seat isn't sealing.

air rushing out the oil fill tube, will happen slightly just from the ring gaps. Large amount of air would indicate larger ring problems. I've done these type of tests before and if the piston was at bottom vs. top I'd get different results.