Internal metal ply on IO540 for Constant Speed Prop
Bob Turner's method is absolutely the way to go!. Do not start banging on the plug to somehow pop it out. Drill a 1/4" hole in the plug center just enough to create a pilot hole for a 3/8" x 3" lag bolt. Just get a simple galvanized lag bolt from hardware store that is inserted through a 2x4 big enough to bridge across the opening diameter (3" or more is enough) and is pre-drilled with a 3/8" hole in the center. You just don't want the threads catching on the wood inner diameter. Use a 3/8" flat washer under the head of the bolt and place the 2x4 surface against the flange. Begin tightening the lag bolt into the pilot hole and be sure have something ready to catch the oil that most likely will come dripping out (unless you like clean up oil puddles like I had on my floor). BTW it's probably smart to vacuum the external metal shavings from the drilled hole before removing the plug to limit the amount that could get into the opening. You'll want to wipe away any shavings to keep them out of your oil system. If I knew what I was doing I'd attach photos, but it is pretty straight forward after you decide to do it this way!
RV10 Builder #40325