Another tip------since you have pretty well proven that its rings sealing, plus other areas of questionable work---------an method of rapid ring seating used by pro stock racers back in early 70s--------put the rear end up on jackstands ( some that will not fall over) and run the engine up thru the rpms a few times--------while applying the brakes!!!!!!!!!!!! this will allow you to put a controlled load on the engine while its reving up----you will have to watch brake temps back there so maybe can only do 2 or 3 before cooling off-----and this is a strong load , not just dragging the brakes a little-------