Hi Nick, my original Manual says: Bore in Block: 46,82 - 46,858 mm Cam Journal: 46,741 - 46,745 mm Clearance: 0,066 - 0,117 mm For the inserting Spitfire MK3 bearings we bored exactly 50,00 mm. Sad to hear the story from the block / line boring. Cheers Martin