The secondary oil pressure relief valve on the side of the engine was eliminated on late model engines. Did that have any effect on low oil pressure at idle? Some have eliminated the spring and replaced it with a rod to prevent it from opening, claiming it raised the oil pressure at low rpm.

Found one of these collapsable copper rods on my GA004310 engine that someone had put in. I'll keep an operational relief valve thank you very much.

I would much rather have a spring exerting a constant force on the piston than a fixed length of copper rod that is subject to a thermal expansion rate that is different than the aluminum case.