Getting that dowel to move after it's been in one position for 60-something years can be a challenge. Pounding on a stubborn dowel pin could drack an otherwise serviceable block. I'd suggest using a good penetrating oil like KROIL (
www.kanolabs.com) with the engine rolled onto its side for a couple of days so the oil can puddle over the plug, followed by moderate heat applied to the block near the dowel with a torch, before trying to drive it into the "full flow" position. I'd also suggest drilling and tapping the dowel for a bolt thread, so a slide hammer puller can be used to reverse the procedure if necessary. If I ever decide to run a full flow filter on the 261 I have with the dual capability, I'm going to pull the dowel out, thread the block for a fine thread bolt, and fabricate a dowel from an Allen head bolt so I can screw the plug in and out, with a jam nut to keep it secure.
That covers the "how"- - - -let's examine the "why" behind the procedure. Full flow oil filtering is far less efficient at keeping oil clean than flowing a small volume of oil through a tightly woven filter medium and removing contaminants that will pass through a full flow filter. In order to flow enough volume to keep the engine lubricated it's necessary to flow a large volume of oil through the filter quickly, so the pores of the filter media must be fairly large. Smaller particles won't be filtered out. For really good cleanup of the oil, an engine should have two filters, a full flow for straining out chunks big enough to damage bearings and/or clog oil passages, and a bypass filter to catch the fine debris. There are some hydraulic fluid filters that can trap particles down to 1 micron in size, much smaller than even a normal bypass filter can catch. Ditto for Diesel fuel filters.
Some carburetors have a fine mesh brass strainer screen at the inlet fitting. Training material from Carter carburetor company used to claim that the screen was there to catch "rocks, marbles, and bowling balls". A full flow filter serves the same purpose for motor oil. For really efficient oil filtering, rum BOTH types of filters.
Jerry
