Thanks Miles n Hatman. Latest update. Ive borrow 3/4 drive impact gun and main brg caps now off nos 2 - 4. Can get upper half out too by using piece plastic shimm to push it round crank - similar to big ends - no catastrophic failure, just shiny portion in centre portion of each shell, no grooving or signs of backing showing thro. Is this bad news or would a small amount of wear on each shell give me low oil pressure at hot tickover? - No it shouldnt - wot yu describe is normal polishing - there are no score marks? With regards to the relief valve spring, how much compression should there be as standard? - that depends on the pump - I am not familiar with the RR one. this one squashes up about 6mm, will check end float on gears. thanks steve If it only squashes 6mm - i wud be reluctant to fit a 6mm spacer - otherwise - no pressure relief - maybe a 3mm spacer if yu can, but yu need to check pressure before and after with a pressure gauge