The downside of the bypass oil filtration system in my mind is that for the significant percent of the time which the oil is not filtered, sediment is falling out and landing on the bottom of the oil pan where it will never be filtered again. Back in the day when these trucks were driven on dirt roads, sucking in dust through the vent slots in the valve cover, you would find as much sludge in the oil pan as you would in the oil filter if you were to remove the pan to look at it
The full-flow filtration system filters 100% of the oil, not giving the chunks much of a chance to settle at the bottom of the oil pan.
Unfortunately the 216 and 235 engines were not deigned to be able to accommodate a full-flow filtration system, while still providing adequate oil flow to lubricate all of the moving parts.
The 261 is designed for the full-flow filtration system, and if I had one, I would set it up to use one.
My 3 cents. (extra typing costs an extra penny. All sales are final. No warranty implied, and no refunds. Even if I am dead wrong.)
Carl
