[Jack Shaft]

Whats interesting in what you are doing is there is an actual rule for shaft/babbit bearings,.001 clearance for each inch of shaft diameter..10 inch shaft?.010 oil clearance.The model a engine journal is best served by setting the bearing clearance at .0015.Using plastigage is a direct measurement.Using aluminum foil is a 'go-no go' method of measurement,use a micrometer and fold aluminum to a thickness of .002,I use a 3/4" square,install in clean bearing cap,torque..if it locks the crankshaft from turning you're good,not as precise as plastigage but will work.I use foil with the engine in the car,plastigage when its on the stand