Also they have combustion chamber designs which are better at avoiding detonation as well.

The key thing in deciding how much CR you can run is what sort of timing the engine is taking, personally I would only ever want to drop the CR on an engine if I was getting down to under about 10 degrees of ignition timing for a significant part of the map.

YB engines dont seem to take timing the way that skyline engines etc do.

Rod's is different internal geometry which helps it and also has very well developed cam profiles that are designed to help it rev, so its quite different to a normal YB.