different valvetrain question

[twentyover]

Using uncaged needles would require hardening the both the crank and the block. Point loadings on rolling element bearing are pretty much huge, and even a cast iron block, with all the carbon in it, is too soft for needle rollers.

Transmission gears usually high nickle with alot of hardening technology thrown at the- for good measure, they have huge loadings to deal with. They are already expensive steel with expensive heat treat, so a needle roller there isn't a big cost impact

 

[MustangSix]

or high pressure air bearings like some turbine engines?

The point of diminishing returns is reached pretty quickly once you depart from plain, old fashioned, oil lubricated, shell bearings.

 

[Lazy JW]

Both International and White built four cylinder truck engines back in the 1930's with two main bearings that were ball type bearings. Yup, all four cylinders were between the mains, the cranks were very heavy and the engines were pretty low powered, but it did work.
Joe