As long as the height is correct, 1/2" difference in diameter won't make enough difference in the filtration to matter. The important specification is the micron measurement of the holes in the paper filtering media. Bypass filters like the old stovebolt units can have VERY fine micron numbers, because the oil does not have to flow through the filter with enough volume to lubricate the engine. An average full flow filter has about 2 or 3 micron holes, indicating particles smaller than 2 or 3 thousandths of an inch will pass through the filter and stay in circulation.
The Frantz bypass filters I used to sell for 18 wheelers fit the LuberFiner 750 canisters, and were rolled out of toilet tissue. They were 1/10 micron rated, which meant they would filter out particles as small as 1/10,000 inch. These filters were not intended to be full-flow capable, but they would clean even the tiniest dirt particles out of the oil. We ran 10,000 miles between filter changes, and never changed the oil. On a 15-gallon system, it usually required 2 gallons to be added during a filter change to replace what was trapped in the cartridge. We had several engines with well over 100,000 miles on the oil, and it still passed spectrometric analysis of the oil samples we took during filter changes.
Jerry
