I have spent some time back on the Rolls Royce Phantom 2 engine and managed to get all the piston rings gapped and installed onto the pistons. In the third photo, the yellow spot is to tell me that the ring is the right way up! and you can just see the piston ring gap at 4. o’ clock set at 12 thou. I then installed all the rods & pistons into the block, castellated big end nuts secured, engine then turned over really smoothly. You may be asking yourself, why has he spotted the big end nuts with yellow paint when he has clearly cotter pinned all the nuts?! The yellow paint is to tell me that the nuts have been set at the correct torque before installing the cotter pins, just in case the phone rang between both operations, it’s an old lesson learnt from my racing car days, leave nothing to chance!