Now that you have it loosened up a bit, a shot of PB-Blaster in the exhaust and venturi will help finish up getting things "Flippy." Like the other guys said, getting something slippery all around the engine now will have benefits. I have found PB-Blaster to be quite good at lubing old engines. it cuts through gunk pretty well. My standard routine with barn fresh old engines, if they don't look too bad, is to heat them with a monokote heat gun for quite q while. Normal castor gunk will start to melt pretty quickly, and once you can turn the engine over with a prop, I give it a shot of PB-Blaster to help finish the job. It clings to the parts well and doesn't get gummy with age.
This works about 99% of the time. I just got two old Fox combat engines last night that were stuck. The gunk looked blackish, like tar. The heat gun trick wasn't working so into the crock pot they went. After soaking on low heat for 24 hours (low heat does get pretty hot!) I pulled them out. They were clean as a whistle, but they still wouldn't turn over. I couldn't see any scoring or scratches in the cylinder, thinking that they might really be seized, but I have never seen a model engine get a piston to seize on a cylinder wall. I finally had to resort to gently heating the cylinders with a propane torch! That finally got that gunk to break down and let the pistons move. Then the PB-Blaster did it's job. I cleaned out a bunch of kibbles and bits of balled up gunk, then re-assembled it. They go "flippidy flippidy" really nicely now! There muct have been some sort of secret sauce oil in the fuel that these engines were fed. It wasn't normal castor oil. I had two Cox .049's out of identical P-40 plastic RTF planes that were stuck one time. Sometimes you can just heat a Cox engine really gently with the heat gun and they loosen up, then flush with fuel. These didn't respond to that treatment. I pulled them apart and found the tanks and crank cases filled with some sort of grayish sludge, almost like modeling clay. The tanks were filled with it! That couldn't have been castor sludge. it cleaned out but was difficult. They went back together and ran fine. Just another times where i wonder just what in the H-E double toothpicks some people tried to run in these things! And don't be surprised if your engine isn't fully broken in. Lots of these old engines we find are pretty low time. Just because they looked like they were run, doesn't mean that they were run very much.Given a few as we control line flyers are, I think we fly way more that a lot of our predecessors did and know a lot more about what under the cowling now.
Type at you later,
Dan McEntee