Quoting myself from my book ("Chevrolet Stovebolt Performance"*), the math using its 2.311" rod journal for this example:
The only leak, or outlet path, for oil pressure in the rod’s journal to bearing clearance space is at the sides of the rod big ends. This annular clearance area is easily calculated. The journal OD is 2.311”; with a bearing clearance of .003” (generous, but possible), the leak area is the bearing ID area minus the journal OD area. Here, it’s 4.205 in2 ((2.311+.003)2 × Π ÷ 4) minus 4.195 in2 (2.3112 × Π ÷ 4).
The leakage from each side of the rod is .0109 in2. The radial clearance between the rod and journal cheek is the surface area of a horizontal cylinder 2.314” OD times the width of the side clearance, or 2.314” × Π × W.
For the side clearance to control the oil escape volume, the side clearance area must be less than the annular clearance; in this case, less than .0109”. If the side clearance area is equal to the known leak at .0109”, W is .0015”, or 1½ thousands. Therefore any value of W higher than .0015” (the rod is .003” narrower than the journal’s cheek-to-cheek width) has no effect on oil pressure or the volume released.
Since the side clearance is always much larger than this, any more clearance is, of course, harmless.

* http://victorylibrary.com/235BK.htm