With original cam, rockers and valve springs, the Triumph six-cylinder engine survives well without cam bearings but as we upgrade these components with higher lift, higher ratio rockers and stronger valve springs, the pressure on the cam is increased and there is more danger of cam journal failure. As a general recommendation I would say cam bearings should be installed for anything over 0.400″ net valve lift. Most automotive machine shops do not have the proper equipment to bore a TR6 block for cam bearings. Bring your block to us or have it shipped, and we will bore it for cam bearings using our own dedicated equipment designed specifically for the job. Price does not include cam bearings, installation of bearings or shipping. Shipping must be arranged by the customer.