Big End lubrication had been compromised by the practice of shimming the Caps - Although found in all Engine reference books and widely practised, consideration needs to be given to the application and purpose of how things are intended to work.

With dipper lubricated big ends it relies on oil being scooped up and forced into the oil ways cut within the bearing. There are troughs cut along the cap joint which is to act as a reservoir and provide lubrication during the remainder of the journal rotation. For this to be effective it needs to be a closed joint, otherwise the oil will just squirt out of the gaps and not be retained for the duration of the rotation.