True, more
oil can only be a good thing for the needle bearings and for cooling the springs.
However, the problem with needle bearings is that they don't restrict the
oil flow like stock rockers or rockers with bushings. The
oil passes through the gaps between the needles very easily.
This can cause the valve covers to nearly fill with oil which can cause a problem if it drains the pan and starves the oil pump. Also, having too much oil in the valve covers can encourage oil getting past the valve guides and blue smoke in the exhaust. So in most cases it is necessary to retrict the oil when using needle bearing rockers.
When you have pressure fed shaft oiling to the friction surface of the rocker (like FE and Mopar engines), needle bearings aren't as necessary as they are with stud mount rockers where the oil is "splash" fed via the pushrods. Needle bearings were first installed in stud mount rockers because the stock rocker balls were burning up under high spring loads. If it had been possible to pressure feed the balls, needle bearings might not have been necessary.
While needle bearings certainly work well with shaft mount, pressure fed systems like an FE engine, a good bushing material works as well and restricts the oil better. (However, I don't care for the aluminum rockers that have neither a bearing nor a bushing. Aluminum is not a great bearing material because if there is even a momentary drop in oil pressure, the aluminum will either gall or wear).
The advantage of a good bushing or needle bearing is that you don't need a constant supply of pressurized oil for things to live. Just a good splash of oil will do and momentary loss of oil pressure does no harm. Needle bearings require even less oil than bushings but have the disadvantage of allowing more pressurized oil to pass through them.
Hybrid Mode
