Wow, interesting!
Living in hilly Dunedin, the same fault is noted with my 4.1. Take the old girl for a serious bash, park it up at my mate Grants steep drive, and oil piddles out the back of the engine. On a flat, no problem.According to the ring makers information for the forged pistons I'm using on my project engine, there is an overwhelming increasing in blowby over 4500 rpm if you use the factory ring settings on the Falcon I6, and certainly if you use the XF style low drag piston rings, there is likely to be a huge amount of blow-by. Ford lowered the readline 300 rpm with this modification in October 1984. 4800 rpm, down to 4500 rpm. Before that, a cast iron headed XD 4.1 could take brief sperts to 5300 rpm.
Most 250 cars run ~3 cfm of crankcaes blowby at 4500 rpm, according to the charts based on blow by per inch of cylinder bore verses ring clearance. It can go up to ~5 cfm! The idea is to set the ring gaps as closest you can without flutter. I'd say with the stock setting, the earlier rope seal is suspect, because it may pick up the total blow by. I'm fairly certain this is why Ford minted the 83 DA block, which had the dog turd main seal when the tighter low drag rings were put in the Falcon in 1984.
Rope seals and the later type can be redone in place, but I'd just monitor it, and see if a hard trash at sub 4000 rpm yields the same problem.
There are technically correct ways of fixing it, if you can't go in an change the ring settings once your engine is built. 54Ford may be aware of the crankcase venturi system used in race cars to crate blow by suction from the scaveging of the exhast. Its just a non return PCV valve that bleads off blow by from the crankcase right to the area below the header tube. In engines that are getting old, it can reduce the work the rings do, stop ring flutter, and deal with the ill afects of blowby. On engines that have issues with oil control, these set-ups are very good.
