Hi wonton, I think your main confusion is the difference in a 'bypass filter' and a 'full flow filter'. A bypass filter takes a small, 1/8" or so, line from the main galley and sends it thru the filter, and then dumps it right into the crankcase cleaning a small fraction of the oil (basically useless in my book). this type of filter does need restriction or you will reduce your oil pressure. A full flow filter, which is what the pin on the 261" is for, takes the oil from the pump side of the galley, sends it all thru a filter, and back into the oil galley (no oil loss). If you have a block with the 1/2" pipe threaded ports and the drive pin, what I would do is run #8AN fittings and line from the pump thru the filter and back to the galley. As I said in my previous post, be sure the pump outlet on the block (forward port) goes into the 'in' side of the filter. Also, if the pin is driven in, you MUST set it up like this (with the large lines)or you will have NO oil flow to the bearings, however if the pin is flush with the block you can still use the large lines and full flow filter, but it will only filter a portion of the oil and with no pressure loss but still look cool. Again, just my experience, Tim II#498
